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What components of sound are used for hearing?

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There are a wide variety of ear structures in terrestrial and aquatic vertebrates and invertebrates. Ears in marine invertebrates and fishes evolved prior to ears in land animals whereas ears of marine mammals evolved from those of land mammals that returned to water and therefore readapted to hearing in water.

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Madeira Island is a paradise for those looking for cetaceans. Discover the types of whales you can see on Madeira Island!

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https://www.eldreds.com/auction-lot/*-whale-s-ear-bone-length-5-._A9643FB9AD

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Film about 52 Herz calling whale

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A cinematic quest from Executive Producers Leonardo DiCaprio and Adrian Grenier to find the "52 Hertz Whale," broadcasting at a frequency that no other whales - or anyone else - can seemingly understand. As the film embarks on its engrossing journey, we uncover what this whale's lonely plight teaches us not only about our relationship to the ocean, but to each other.

304 IMDb 6.5 1 h 36 min 2021

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A cinematic quest from Executive Producers Leonardo DiCaprio and Adrian Grenier to find the

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A spectrogram of the 52-hertz signal

The 52-hertz whale, colloquially referred to as 52 Blue, is an individual whale of unidentified species that calls at the unusual frequency of 52 hertz. This pitch is at a higher frequency than that of the other whale species with migration patterns most closely resembling the 52-hertz whale's - the blue whale (10 to 39 Hz) and the fin whale (20 Hz). Its call has been detected regularly in many locations since the late 1980s, and appears to be the only individual emitting a whale call at this frequency. However, the whale itself has never been sighted; it has only been heard via hydrophones. It has been described as the "world's loneliest whale", though potential recordings of a second 52-hertz whale, heard elsewhere at the same time, have been sporadically found since 2010.

52 Hz is equivalent to the musical note G#₁, which is the 12th lowest key on a conventional 88-key piano keyboard; or, the 4th finger position on the lowest string (E ₁) of a double bass.

The sonic signature is that of a whale, albeit at a unique frequency. The call patterns resemble neither blue nor fin whales, being much higher in frequency, shorter, and more frequent. Blue whales usually vocalize at 10-39 Hz, fin whales at 20 Hz. The calls of this whale are highly variable in their pattern of repetition, duration, and sequence, although they are easily identifiable due to their frequency and characteristic clustering. The calls have deepened slightly to around 50 hertz since 1992, suggesting the whale has grown or matured.

The migration track of the 52-hertz whale is unrelated to the presence or movement of other whale species. Its movements have been somewhat similar to that of blue whales, but its timing has been more like that of fin whales. It is detected in the Pacific Ocean every year beginning in August-December, and moves out of range of the hydrophones in January-February. It travels as far north as the Aleutian and Kodiak Islands, and as far south as the California coast, swimming between 30 and 70 km (20 and 40 mi) each day. Its recorded distance traveled per season has ranged from a low of 708 km (440 mi) to a high of 11,062 km (6,874 mi) in 2002-03.

Scientists at the Woods Hole Oceanographic Institution have been unable to identify the species of the whale. They speculate that it could be malformed or a blue whale hybrid. The research team is often contacted by deaf people who wonder whether the whale may also be deaf.

Whatever biological cause underlies its unusually high frequency voice does not seem to be detrimental to its survival. The whale's survival and apparent maturity indicate it is probably healthy. Still, its call is the only one of its kind detected anywhere and there is only one such source per season. Because of this, the animal has been called the loneliest whale in the world.

Calls picked up by a sensor in California in 2010 suggest that there may be more than one whale calling at 52 Hz.

Approximate map of the 52-hertz whale's migration range

The 52-hertz whale was discovered by a team from the Woods Hole Oceanographic Institution. Its call was first detected in 1989, then again in 1990 and 1991. In 1992, following the end of the Cold War, the U.S. Navy partially declassified the recordings and technical specifications of its SOSUS anti-submarine hydrophone arrays, and made SOSUS available for oceanographic research. As of 2014, the whale had been detected every year since.

The Loneliest, a short mockumentary film about two women searching for the loneliest whale, was made in April 2014 by Lilian Mehrel, with the Alfred P. Sloan Foundation.

The title of the Taiwanese movie 52Hz, I Love You (2017) is inspired by the whale, using it as a metaphor for the loneliness experienced when looking for love.

The animated short film entitled The Phantom 52 premiered at the Sundance Film Festival in January 2019. The film is written and directed by Geoff Marslett, and stars Tom Skerritt as the loneliest whale. The Phantom 52 went on to play at over 60 film festivals worldwide and win a half dozen awards.

A feature-length documentary entitled The Loneliest Whale: The Search for 52, directed by Joshua Zeman, the director of , and executive producers Leonardo DiCaprio and Adrian Grenier, was commercially released by Bleecker Street on July 9, 2021. The film follows Zeman and a group of five scientists and oceanographers on a quest to find the whale off the coast of California. Funded through a Kickstarter campaign, the film received generally positive reviews among critics, holding an approval rating of 86% based on 35 reviews on Rotten Tomatoes. Time's Stephanie Zacharek called the film "both invigorating and calming to watch," while Katie Walsh wrote in the Los Angeles Times that the film is "a modern-day Moby Dick with a conservationist bent" that "surprises, delights and will keep you on the edge of your seat." Sheri Linden of The Hollywood Reporter wrote that "the film's epilogue caps the action with a rapturous surprise", referring to the sighting - complete with film footage - of a blue whale- fin whale hybrid, believed to be the source of the 52 Hz calls.

Montreal-based saxophone player and composer Colin Stetson's 2013 album New History Warfare Vol. 3: To See More Light included a song entitled "Part of Me Apart From You". Though not explicitly written about the 52-hertz whale, when first performing the song live, he has remarked on at least several occasions that the story of the "loneliest whale" resonated deeply with his composition. "This whale is alone in a large body of water, swimming, singing its song, calling for a likeness it will never find," he said by way of introducing the song at a performance at Toronto's Great Hall on 19 May 2013. "When I play this song, I can't help but think about this whale, who right at this very minute is singing alone."

South Korean group BTS's 2015 album The Most Beautiful Moment in Life, Pt. 2 includes the track "Whalien 52", which explicitly uses the 52-hertz whale as a metaphor for the alienation from others often felt by adolescents.

The English folk duo Kathryn Roberts and Sean Lakeman included the song "52 Hertz" on their 2015 album Tomorrow Will Follow Today. The song is about the whale and includes the line, "52 Hertz, 52 Hertz, I'm singing a love song that no-one can hear" in the chorus.

Chinese metal band The Samans's song "Whalesong" from their eponymous 2012 album is about the whale, using the lyrics "52 Hertz of heartbreak, 52 Hertz of heartache".

British-Portuguese band Moby Dickless and their song "52 Blue" uses the whale as a metaphor for alienation and loneliness. The lyrics were written by lead singer, Sloth and were inspired by his experience living with autism as well as his insecurities about being a frontman/Vocalist. The single artwork, designed by Bart D'Angelo, features a depiction of the whale in a box surrounded by lonesome images of boats.

"52 Hertz Whale" is a Slovak band based in Bratislava, Slovakia. The group debuted in 2015 with the eponymous EP. Later they also released a studio album called "I've met a lot of people". Group performed at the Pohoda, Grape and Colors of Ostrava festivals, and also performed in front of bands such as Algiers, The Underground Youth, Les Discrets, The Physics House Band and Soviet Soviet.

In 2022, the American artist and musician "Crywolf", in his album Exuvium, released [52hz], which is assumed to be a reference to the 52-hertz whale, as the only words pronounced in the song are the sentence "Darling, you're still alone", told several times.

In 2020, Japanese novelist Sonoko Machida published a novel titled 52-Hertz Whales, in which the anomalous whale serves as a metaphor for "voiceless" lonely people who find each other by chance.

In 2014, American writer Leslie Jamison published an essay in The Atavist Magazine about the 52-hertz whale's popular appeal as a metaphor for loneliness and perseverance. The piece was later included in Jamison's 2019 essay collection Make It Scream, Make It Burn.

1. "Blue Whale". Bioacoustics Research Program. The Cornell Lab of Ornithology. Archived from the original on 26 February 2015.

2. Watkins, William A.; Daher, Mary Ann; George, Joseph E.; Rodriguez, David (December 2004). "Twelve years of tracking 52-Hz whale calls from a unique source in the North Pacific". Deep Sea Research Part I: Oceanographic Research Papers. 51 (12): 1889-1901. doi:10.1016/j.dsr.2004.08.006.

3. Nelson, Bryan (20 May 2012). "52 Hertz: The Loneliest Whale in the World". Animal Planet. Discovery Communications. Archived from the original on 24 December 2013.

4. ^ Anderson, Ben (5 January 2011). "'World's loneliest whale' pays visit to Alaska". Alaska Dispatch. Archived from the original on 24 November 2012.

5. ^ Revkin, Andrew C. (17 February 2015). "Filmmakers Set Sights on '52', the World's Loneliest Whale". The New York Times.

6. ^ "The Loneliest (a short film by Lilian Mehrel)". Archived from the original on 1 March 2015.

7. ^ Benjamin, Jeff (2 December 2015). "BTS Succeeds With Mixed Styles, Emotions on 'Most Beautiful Moment in Life, Pt. 2'". Billboard.

8. ^ Yoshikawa, Akiko (10 January 2021). "「52ヘルツのクジラたち」町田そのこさんインタビュー 虐げられる人々の声なき声をすくう" [52-Hertz Whales: An Interview with Sonoko Machida-Uplifting the Voices of the Downtrodden and Voiceless].

9. ^ Jamison, Leslie (2019). Make it Scream, Make it Burn: Essays. New York: Little, Brown and Company. pp. 3-27. ISBN 978-0316259651.

Jamison, Leslie. (2019). "52 Blue" in Make It Scream, Make It Burn: Essays. New York: Little, Brown and Company.

Watkins, William A.; Daher, Mary Ann; Reppucci, Gina M.; George, Joseph E.; Martin, Darel L.; DiMarzio, Nancy A.; Gannon, Damon P. (2000). "Seasonality and distribution of whale calls in the North Pacific" (PDF). Oceanography. 13 (1): 62-67. doi:10.5670/oceanog.2000.54. Archived (PDF) from the original on 29 April 2019.

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The 52-hertz whale, colloquially referred to as 52 Blue, is an individual whale of unidentified species that calls at the unusual frequency of 52 hertz. This pitch is at a higher frequency than that of the other whale species with migration patterns most closely resembling the 52-hertz whale's - the blue whale (10 to 39 Hz) and the fin whale (20 Hz).

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Recommeded by Marko - available on Amazon or Curzon

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Acclaimed director Wim Wenders presents an affectionate portrait of Portugal's capital city in this engaging and beguiling drama. Rüdiger Vogler once again returns to the role of Phillip Winter (Kings of the Road), a sound recordist who travels to Lisbon to help a friend on the making of his film, only to discover he has disappeared without a trace.

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Self-Assessment Manikin (SAM) for valence, arousal, and dominance.

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https://www.pamguard.org/

If I was interested, Marko suggested I could download and try out with recordings I will make - but maybe not a priority. Marko has heard of it but niit used it.

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Soundscape ecologists also study the relationships between the three basic sources of sound that comprise the soundscape: those generated by organisms are referred to as the biophony; those from non-biological natural categories are classified as the geophony, and those produced by humans, the anthropophony.

Acoustic ecology is more concerned with human perception of soundscapes (R Murray Schaeffer et al.)

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Silence - Stillness - Destruction @ Death

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Silence - Stillness - Destruction @ Death

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Karen Barad on the atomic bomb. The hibakusha are those who experienced the explosions in Japan. Something here about silence and sound.

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Find out what all this means....

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Insights into the soundscape 'under the sea'

Pilot whale whistles and echolocation clicks, from Laura Redaelli's research
Throughout the ages, Disney has created many a film that isn't historically or scientifically accurate. The recently-released version of The Little Mermaid is no exception. Of the many fictional elements of this film you'll no doubt have spotted if you took your children or just your incurably-ocean-loving-self to see it (e.g. that sharks are highly unlikely to burst through a shipwreck in pursuit of prey, for instance), there's one thing that this movie gets scientifically spot-on: the ocean is a place alight with sound, harmony and highly-choreographed music.

When we on land think about the ocean's sounds, most of us think of breaking waves. A few might also mention the lonely song of a humpback whale. But the ocean is awash with sound - countless frequencies, patterns and intensities are created by marine life to communicate, navigate, find prey and attract mates all the time in the ocean. Although few humans to date have the opportunity to regularly listen to and appreciate the performance, the live-action musical of the ocean is playing now and forever, in underwater theaters everywhere.

Sea critters have likely evolved to use sound so much because sound waves travel really well in water. In contrast to light, which travels slower in water than in air and is further hampered by the ocean's multitude of suspended particles (visibility in very clear water might be 150-200m), sound waves travel around 5x faster in water than air. Much of aquatic life takes advantage of this efficiency by creating and being highly sensitive to sound.

Laura Redaelli deploying an acoustic recorder on a research trip
Laura Redaelli, one of our PhD students at MARE-Madeira, is focusing on sound for her PhD, and particularly those sounds from marine mammals. She is currently building an acoustic library of marine mammals around Madeira - the first of its kind for the island. Laura and our Marine Megafauna team regularly go out to collect acoustic data, pairing recordings from a hydrophone with sightings of species and their observed behaviors. This catalog can hopefully be used to profile sounds when acoustic data is collected independently of sightings, from acoustic recorders deployed in various locations around the Madeira archipelago.

Regularly recording calls and clicks from Madeira's resident and migrating mammals, Laura gets an insight into the vast variety of sound these animals make. For the newcomer to this soundscape, Laura explains, "There are two big groups of whales, commonly known as toothed whales and baleen whales, and they have very different ways of communicating. Baleen whales produce these very low-frequency sounds, starting from a few hertz (Hz) that we can't even hear (we hear sounds above 20 Hz) up to a few hundred Hz. Blue whales, for example, are around 20 Hz and we can't hear them. So when I analyze their recordings, I have to speed up the sound to hear their calls."

One of the cool features of baleen whales is that they can communicate over huge distances. "The lower the frequency, the farther sound travels, which means that some of the baleen whales can communicate over very, very long distances," Laura says. Five hundred miles is well-recorded for a few species, with some studies suggesting that even a thousand miles is possible when these animals take advantage of a unique sound channel underwater.

Sperm whale social clicks (called codas), from Laura Redaelli's research
"The other group is the toothed whales, which includes sperm whales, pilot whales, dolphins and relatives," Laura continues. "They produce higher frequencies; we're talking thousands of Hz. Some of them produce ultrasounds that we can't hear either, because we can't hear above 20,000 Hz. To listen to these recordings, I have to slow them down."

One of the well-known sounds that toothed whales make are whistles, like those frequently associated with dolphins. These are their social calls. Something that some toothed whales can do that you might not know about is echolocation. "They send out narrow-band clicks that cover a huge frequency range over a very short time. They use these clicks to locate prey and navigate, listening for the backscatter of the sound to essentially get an acoustic image of what's around them," Laura explains. This is basically how naval sonar works.*

Most readers will likely be aware that whales and dolphins communicate by songs and whistles, but did you know that fishes make distinct calls, too? Enter Sebastian Muñoz, one of our collaborators who's doing the International Master of Science in Marine Biological Resources (IMBRSea) and conducting research at the University of Lisbon. Similar to Laura, Sebastian is creating an acoustic catalog for Madeira, but his catalog is focusing on fish and the Mediterranean monk seal.

Recovering an underwater acoustic recorder (hydrophone). Photo provided by Sebastian Muñoz
Sebastian's growing catalog of fish and seal recordings is the first attempt to characterize and create a library of these sounds in Madeira. "Madeira is a place with a lot of diversity in the ocean, which is very, very important. It's the kind of environment, in the open sea, that can attract many species. It's also home to one of the last remaining populations of Mediterranean monk seal, which is the most endangered seal species in the world," he explains of his decision to focus his research here.

Stand alone, acoustic libraries add an important layer to our understanding of a species' behaviors. But they also have important applications for wider research and conservation. "By doing this research, we can offer another way to monitor these species, to complement other sampling techniques," Sebastian explains.

This sort of monitoring is known as Passive Acoustic Monitoring (PAM) and it has two key advantages. One, it's non-invasive. If you know the sounds an animal makes, you don't have to tag it or step into its environment to monitor it. This is great for conservation, as usually the less humans interfere with recovering wildlife, the better. Two, it's cheaper. Leaving a hydrophone underwater for a few months costs far less than hiring SCUBA equipment or divers to monitor marine life over the same time period! Underwater video recordings are also more expensive (regarding equipment, energy and data-storage expense). Which means that, for marine research institutes like MARE-Madeira that are prioritizing low-cost research solutions, audio recordings are a real plus.**

Our in-house Marine Technology and AI team ( Wave Labs) has also identified a third (potential) advantage of acoustic monitoring: ecotourism. Whale watching is a huge industry worldwide and is particularly popular in Portugal, accounting for about a quarter of European whale-watching revenues. In Madeira, regulations have been in place since 2013 and significant efforts have been made by companies here to make this activity as sustainable and respectful to the whales as possible. Whale watching in Madeira also greatly aids marine research: our long-standing relationships with whale-watching companies has helped us gathered important data on cetacean species - we'd know much less about these elusive animals without our whale-watching partners. As more tourists come to Madeira and these companies grow, however, they are faced with a dilemma: more tourists means more boats, which means more underwater sound and, potentially, more whales avoiding that sound. Growth in our whale-watching companies is important for Madeira's economy, global ocean literacy and marine research, so the question is: what are the ways this industry can grow without creating more sound pollution? Marko Radeta, our Marine Technology and AI team leader, together with researchers from the University of Lisbon and the University of Madeira, has devised a possible, complementary solution for whale-watching companies: whale listening.

With our partners, we designed and developed an easy-to-use whale-listening app ( Android, iOS) and a low-cost, lightweight hydrophone. We then trialed both in whale-watching tours. The result was great for both tourists and scientists, as we were able to collect valuable data from the whale-watching tourists and the tourists were able to hear the whales they were watching! It got great reviews. To our knowledge, this experiment was the first attempt to create a general-purpose system for collecting and streaming sounds while whale-watching. Although this system has only been used on-board whale-watching vessels to date, having a purely whale-listening alternative could help bring these animals to life to many more people on shore, costing less and reducing the amount of sound we collectively create in the ocean, too.

Images from our low-cost whale-listening app and hydrophone!
We'll end this article on a positive note(!), but no discussion on ocean sound would be complete without properly acknowledging the wide range of sounds made by humans underwater, and their impacts. In a nutshell, the noise we add to the ocean soundscape reduces the range over which marine life can communicate, reduces their hearing abilities and negatively impacts their navigation. From mass strandings of beaked whales after naval sonar tests, to the reduced range of fin whales' calls from 600 miles to 6 miles in heavily-trafficked waters, to beached dolphins showing significant hearing loss, studies repeatedly show that our underwater noise is impacting the sensing, communication and thus survival of these animals. Our noise also has a negative impact on our own industries, like fishing and tourism, as it can detract wildlife. "When there's a lot of noise and animals figure out they can't transmit messages, some will become silent. Others will move away," Laura explains.

In this week's Blue Economy and Sustainable Islands Forum, hosted by Island Innovation here in Madeira, we're participating in a cross-stakeholder workshop to raise the challenge of sound management in the ocean. How can our underwater industries - those that aid important freight, energy and tourism industries - continue to grow without growing in underwater noise? Is it possible?

We hope you've enjoyed learning a little bit more about the sounds below the waves. May it inspire you to stick your head underwater when you're next in the ocean and listen for a bit! No ticket needed, no Spotify subscription required, just take a deep breath and you can hear the real live-action version of 'Under the Sea'. (Just maybe save the popcorn for later...)

*Learn more about the research we're doing comparing the backscatter of plastics versus deep-sea squid species (an effort to understand why so many deep-diving whales fall victim to plastic ingestion) in this article: https://mare-madeira.pt/choose-rugby-not-plastic/ ** "Especially with our Wave team that has found ways to reduce the cost of recorders from a market price of around €2,000 to our in-house price of €100," mentions João Pestana, our research technician.
Special thanks to Laura Redaelli, Sebastian Muñoz, João Pestana and Marko Radeta for their contributions to this article!

Learn more here!

Nunes, N J, Radeta, M, Nisi, V. (2020). Enhancing Whale Watching with Mobile Apps and Streaming Passive Acoustics. In: Nunes, N.J., Ma, L., Wang, M., Correia, N., Pan, Z. (eds) Entertainment Computing - ICEC 2020. ICEC 2020. Lecture Notes in Computer Science, vol 12523. Springer, Cham. https://doi.org/10.1007/978-3-030-65736-9_18

Radeta M, Nunes N, Vasconcelos D, Nisi V. (2018). POSEIDON - Passive-acoustic Ocean Sensor for Entertainment and Interactive Data-gathering in Opportunistic Nautical-activities. In Proceedings of the 2018 Designing Interactive Systems Conference (DIS '18). Association for Computing Machinery, New York, NY, USA, 999-1011. https://doi.org/10.1145/3196709.3196752

Radeta et al. (2020). INTERAQUATICA-Designing Interactive Aquatic Experiences with Geodesic Domes In-the-Wild. In ACM International Conference on Interactive Media Experiences (pp. 170-173). https://doi.org/10.1145/3391614.3399395

Roberts, Callum. (2013). Ocean of life: how our seas are changing. London, Penguin.

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We got the spirit, you got to hear it! - MARE-Madeira

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Curious about why and how animals in the ocean communicate? Or how we can hear them? Tune in to learn more!

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READ THIS NEXT! Detail on Poseidon project

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READ THIS NEXT! Detail on Poseidon project

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Choose Rugby, Not Plastic - MARE-Madeira

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On a survey trip around Madeira, our MARE-Madeira researchers found a pod of dolphins playing with plastic. Catching it with their tails, the dolphins were passing this plastic between each other like a toy. And when we tried to intercept one of those ‘passes’, the dolphins wouldn’t let us…

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The Butterfly: Communicating with cetaceans

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The Butterfly: Communicating with cetaceans

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Steam punk wooden flip book linked to real time sensor from dorsal fin of an animal.

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Base screws on and can attach a go pro, but provides battery plus usb can connect to external power source

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Frontiers in Environmental Science | Environmental Informatics and Remote Sensing

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This section explores the creation, collection, storage, processing, modelling, interpretation, display and dissemination of data in the environmental sciences.

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Image of the transparent file of extinct whale labyrinth in this article

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Image of the transparent file of extinct whale labyrinth in this article

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https://www.researchgate.net/publication/308122066_Morphological_variation_among_the_inner_ears_of_extinct_and_extant_baleen_whales_Cetacea_Mysticeti

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Figure S16. Three-dimensional model of the digital endocast of the bony labyrinth of CCNHM 1000. 

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Digital endocast of bony labyrinth of small odontocete

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Digital endocast of bony labyrinth of small odontocete

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Electronic Supplementary Material for “Evidence for convergent evolution of ultrasonic hearing in toothed whales (Cetacea: Odontoceti)” Authors: Rachel A. Racicot, Robert W. Boessenecker, Simon A.F. Darroch, Jonathan H. Geisler

CCNHM-1000 is a small odontocete skull including partial premaxilla, maxilla, nasals, frontals, left lacrimal, left jugal, parietals, left alisphenoid, left squamosal, petrosals, left stapes, incus, and malleus, fragments of tympanic bullae, and five teeth and fragments. Locality and Age CCNHM 1000 was collected by James L. Goedert from near the mouth of Murdock Creek (Field Number JLG-76) on April 26, 1986.

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https://www.whoi.edu/oceanus/feature/how-to-see-what-whales-hear/#:~:text=Some%20whales%20hear%20well%20down,for%20humans%20is%2016%20kilohertz.

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Prototype for tidal sonification tactile interface

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Unsound Landscapes, Beastly Soundscapes (2021)

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Unsound Landscapes, Beastly Soundscapes (2021)

How does sound and soundscape composition participate in setting boundaries between humans and animals? Can soundscape compositions be made for the animal world as the primary listener?

This audio/visual essay attempts to address these questions by focusing on the impact of railway infrastructure on more-than-human realms. More specifically, the piece attempts to inspect an inconspicuous, yet beastly invention known as UOZ 1 or Animal Protection Device. It is a set of loudspeakers designed by a Polish company NEEL to create a sonic boundary along the railway as to keep forest animals from crossing the tracks. Needless to say, by protecting animals from colliding with approaching trains, this sonic boundary simultaneously (and, perhaps, primarily) protects human infrastructure and sustains its dominance.

The sound installation is set to broadcast a meticulously designed soundscape composition - a collage made of sounds of animals in distress - each time a train approaches a particular part of the forest. This invention is a starting point to discuss what constitutes beastliness if we focus on sound as a vector of power relations between humans and animals.

The project also brings to the fore the work of Simona Kossak, a professor of forest science who passed away 14 years ago. Kossak spent most of her life living in the Bialowieza Forest in Poland, where she committed herself to learn and understand the psychology of wild animals. Her research contributed to the development of the "key stimuli simulation" which was subsequently used to compose the sequence of alarming signals for the UOZ1. This strand of her research allows us to consider Simona Kossak's work as not only pioneering in the field of acoustic ecology in this part of the world, but also provokes us to rethink the concept soundscape and soundscape composition if we acknowledge the fallacy of boundaries between culture and nature.

The piece was commissioned as an audio paper for Glissando, a Polish magazine dedicated to contemporary music and sound art. It was featured among others in an issue dedicated to rethinking Acoustic Ecology. Original version, entitled "Soundscape as a border. On Acoustic Boundaries, the Theatre for Animals and Simona Kossak" (in Polish only), can be listened here

On September 10, 2021, the piece was presented as an audio/video essay in collaboration with Girilal Baars at Beastly Landscapes Symposium organized by Newcastle University Institute for Creative Arts.

Video essay

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Unsound Landscapes, Beastly Soundscapes (2021)

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Introduction

Over the last three decades, significant progress has been made in quantifying the signal characteristics and global variation of low-frequency sounds produced by blue whales, Balaenoptera musculus spp 1,2,3,4,5. Baleen whale vocalizations in general are low frequency (<1000 Hz)1, 5,6,7,8 and have been related to a variety of behaviors including feeding, navigation, mate attraction, and aggression. As low frequency sounds travel much farther than high frequencies before attenuating, baleen whales likely use low frequencies to communicate over long distances. Environmental factors such as an increased ambient noise from human activities may impact the range over which low frequency sounds can be detected14. Recent studies of blue whale calls suggest this has resulted in lowering the fundamental frequencies of calls over time, although several other factors have also been invoked such as increased blue whale population density or a gradual decrease in mean vocalization depth3, 15. The source of low frequency calls produced by a blue whale is currently thought to be resonance of the cavity spaces in the animal's upper respiratory system16,17,18,19 which implies that body size is proportional to the frequencies generated (the larger the resonating organs, the lower the frequency of sound produced)1, 2, 18, 19. Therefore, understanding the internal physical processes behind sound production in blue whales, and how they regulate their call frequencies, provides important insights into how blue whale populations respond to environmental stressors such as increasing ocean noise. Since all blue whale populations are currently listed as endangered by the IUCN red list20, gauging blue whale response to changing marine environmental conditions is of utmost importance for their conservation.

Blue whale call structure and resonance models

Blue whales have a distinctive call repertoire, with significant variability among populations. For example, northeastern Pacific blue whale calls (one of the best-studied studied populations) can be divided into four fundamental types, A, B, C, and D calls18. The A call, typically the first in a call series, consists of ~20 individual pulses less than 1 sec apart subdivided into multiple non-harmonic components (Fig. 1). The B call is a tonal harmonic signal typically 10-20 sec in duration with a fundamental frequency that steps down between 20 and 16 Hz (Fig. 1). The C call, is a 9-12 Hz upswept tone that precedes the B call. These three calls are often produced together in a pattern. The D call is a highly variable 80 to 30 Hz downswept signal 2-5 sec in duration that is often produced as a counter-call and not produced with the other call types. The B call has traditionally been used to constrain sound production models because its long duration means the source mechanism is unlikely to involve re-circulated air to make the call3. B calls have reported source levels of up to 190 dB re 1 μPa based on recordings made off California21 most of the energy is in the first and third harmonics, where the energy distribution between the first and third is variable and either can be the most energetic in a given call.

Top diagram shows location of hydrophone mooring (red triangle) ~8 km off the coast of Newport, Oregon. Seafloor depth contours are labeled. Bottom diagram shows example spectrogram of blue whale A and B calls recorded on the hydrophone (8 kHz sample rate) on 28 September at 01:57z (27 September at 18:57 PST). Bathymetric map was created using ArcGIS, [version 10.0], ( http://www.esri.com/software/arcgis) software (Environmental Systems Research Institute) from a 100 m resolution xyz file of multibeam depth measurements, collected in 2011 by C. Goldfinger (Oregon State University, Active Tectonics Lab).

Many questions exist with regards to the physics of baleen whale sound production mechanisms. Early work concentrated on bubble resonance, where a given volume of air (encased in an organ or chamber within the whale) at a given depth resonates at a fundamental frequency proportional to the chamber size16, 17. Aroyan et al.18 proposed that blue whales produce sound by a monopole source oscillation of an air-filled cavity, and the animal's anatomy suggest that calls are due to Helmholtz resonance (i.e. resonance caused by airflow over an opening in a cavity or chamber), which allows for efficient constant frequency sound production over changing depths. There are many possible internal mechanisms for blue whales to radiate sound into seawater, where the oscillating source could be made of water, bone, or air. However, sound production systems that involve compressing water or dense tissue require much higher differential pressures and are therefore less efficient than air-filled systems18.

The primary energy source to cause airflow over a cavity or chamber would be the change in pressure produced as the animal rises and descends in the water column as it provides the volume displacements needed to produce the B call3, 18. It is generally assumed no air escapes from baleen whales during sound production23 because this would imply that water could enter the respiratory system and thus eliminate the whales' ability to make the observed call series. The volume of air that can be held by adult blue whale lungs has been estimated at 2000 liters3. While a blue whale can provide a slight change in pressure through muscular compression of the lungs, it is unable to produce the 10 Bars of differential pressure at the sea surface needed to move this volume of air to the upper respiratory system18. Moreover, it seems likely that blue whales produce B calls only during ascent, eliminating the need to produce the positive differential pressure with its lungs that would be required during descent18. However, a study by Oleson et al.24 showed that the average change in depth during calling was <2 m, and therefore the animals are relatively stationary within the water column while vocalizing. Thus blue whales may not need to rise in the water column to reduce hydrostatic pressure and enable vocalizations. The lung volume assumed here would limit B call production depth to 90 m, which is consistent with field observations that indicate B calls are made at <30-40 m depth, while maximum dive depths are estimated to be 300 m25. Air flow rates have been estimated at 25-50 l/s based on resonance quality factors and duration of B calls18.

Anatomical sources of sound

Previous studies have provided detailed anatomical information of the upper respiratory tract of baleen whales and used this as a basis to propose mechanisms for how baleen whales may produce their calls26,27,28,29,30,31. For example, in humpback whales, specific anatomical components and vocal production mechanisms have been related, and modeled, to show their relationship to particular acoustic call characteristics. The source of vocalizations produced by baleen whales is thought to be via airflow within the respiratory system (Fig. 2a,b), where two symmetric lungs are connected to the trachea, a short, broad cone-shaped canal. In the laryngeal region, there are three respiratory valves: the epiglottis, the corniculate flaps and the U-fold. The U-fold possesses some strong similarities to common mammal vocal folds19, particularly in regards to its geometrical dimensions (length to thickness ratio) and slit-like glottal shape, tissue composition (presence of a thin mucosa in the outermost layer), and associated laryngeal muscles and cartilages (e.g., presence of homologous thyroid and arytenoid cartilages)29. Anterior to the U-fold (toward the nasal passages) is the epiglottis, whose valve function is to protect the lower respiratory system from foreign bodies (mainly water), and the corniculate cartilage flaps (Fig. 2a) characterized by its long shape, the high elasticity of its tissues, and the proximity of its two symmetric lips. The laryngeal sac can be seen as a soft extensible oval balloon with an extensive surrounding musculature. Opposite to the laryngeal sac, the nasal region is composed of the nasopharynx, a short flexible region of muscles and soft tissues, and two tube-like parallel nasal cavities with rigid walls which have thick plugs at the dorsal opening of the skull.

Schematic diagrams showing ( a) generalized upper respiratory structures in a baleen whale (after Reidenberg and Laitman 19), with specific location and relative position of respiratory valves (after Cazau et al.29) in the attached insert. (reproduction permissions granted by John Wiley & Sons, Inc. and AIP Publishing LLC) and ( b) simplified sound source model based on structures in ( a) (after Aroyan et al.18; permission granted by Springer publishing), ( a) Red area shows upper respiratory tract including nasal passages and trachea; purple shows the digestive tract; pink shows the laryngeal sac or lumen; green shows the air inflated borders of laryngeal sac; white shows midline, cricoid and thyroid cartilages; light blue shows the vocal or U-fold; the insert shows the position, relative to the U-fold, of the two other respiratory valves present in the laryngeal region (epiglottis and corniculate cartilage29) that also contribute to controlling airflow. Sound is thought to be produced by airflow from the lungs, through the oscillating, respiratory valves (the U-fold) then flow through the laryngeal sac and nasal passages. In the pulse model proposed here, repeated rapid adduction and dorsal elevation of the U-fold vocal process, against the cricoid cartilage, causes pulsed (restriction and release) airflow from the trachea to upper respiratory structures. Sound production likely originates by combining valve states and air recirculation by the lungs and the laryngeal sac through two opposite functions. The U-fold edges and laryngeal sac walls may also vibrate with airflow, potentially amplifying pulses. Laryngeal sac pulsed inflations may also cause pulsed distention of ventral throat grooves, facilitating sound transfer into water.

It is thought that the mechanism for low frequency sound production in baleen whales involves generating fundamental frequencies via U-fold vibration, followed by sound quality modification through variation of laryngeal parameters (by means of muscle contractions), and then sound transduction by means of laryngeal sac wall vibration to ventral throat pleat pulsations impinging on the surrounding water column. Sound production likely originates by combining respiratory valve states (open when an airflow can pass through it, or closed otherwise) and air recirculation by the lungs and the laryngeal sac through two opposite functions (i.e. storing the incident airflow or emitting it back in the respiratory tractus)29, 30. This system would provide the air volume displacements needed to produce blue whale B calls whether or not the animal rises, descends, or remains relatively stationary within the water column. The strong muscular structures surrounding both the laryngeal sac and the lungs (i.e., respectively, abdominal muscles, the diaphragm, and the intercostal muscles) should pressurize the system to a specific pressure different from the depth related ambient pressure and allow it to withstand large variations in hydrostatic pressure while diving and surfacing. Thus airspaces inside the whale may be largely undisturbed by the changes in hydrostatic pressure with changes in the depth of the animal29.

The U-fold appears to be homologous to the vocal folds of terrestrial mammals based upon position, attachments, and composition19. Although oriented parallel to the airflow (versus the perpendicular vocal folds of terrestrial mammals), it nevertheless appears to have a similar function in airflow regulation and pneumatic sound generation. The U-fold structure is thick, lip-like, with numerous closely packed folds separated by narrow and often deep, irregular grooves, supported by arytenoid cartilages, and controlled by skeletal muscles19. This configuration of the folds is thought to lend great flexibility to the surface of the U-fold, permitting movements in different planes as well as the capability to stretch extensively and recoil back to the folded shape. When the lateral walls of the U-fold are approximated, they resemble two opposed lips. Airflow though the gap surrounded by the U-fold may cause the edges of these lips to vibrate, generating sound19. The U-fold's orientation in the laryngeal lumen allows it to serve as a valve to narrow or seal the passageway for airflow between the upper and lower respiratory tracts. A thick, rigid U-fold may be expected, because thicker structures correlate with generating lower frequencies, and mysticetes vocalize in the low frequency range19. Thus, U-fold movements probably control sound output by varying U-fold thickness, length, tension, and the size of the gap between the U-fold's lateral walls19. This movement of the U-fold structure has been invoked as another possible resonant source of sound in baleen whales where changes in vocal fold stretch/recoil (length, tension, and thickness) are necessary to achieve different frequencies. However, U-fold adduction/abduction and elevation/depression also control airflow and therefore the muscles that regulate the tension of the U-fold could control the production of short duration bursts of air, or pneumatic pulses, during airflow from the lungs to the upper respiratory passages or back from the laryngeal sac. A recent study modeling sound production sources of vocal nonlinearities in humpback whale songs31, show that fundamental frequency modulations are obtained by increasing (gradually) the stiffness factor of each side of the U-fold through modeling of the laryngeal muscle activity that controls the U-fold tension.

Methods and Acoustic Vocalization Models

The fundamental frequency and overtones of a blue whale B call are thought to result from similar mechanisms proposed for humpback whales29,30,31,32, that is mainly from resonance due to flow of air through the U-fold, where flow induces self-oscillation of the U-fold leading to resonance whose spectral energy is then modulated by the nasal cavities and laryngeal sac. Early bio-acoustic signal-analysis research by Watkins33 showed that the variable repetition rate of sound pulses can be used to explain the harmonic frequency and spacing of dolphin clicks (e.g. Tursiops truncatus) and toadfish grunts ( Opsanus tau). Moreover, it is known from seismo-acoustic source studies that a series of short duration pneumatic bursts, rather than Helmholtz resonance, can result in harmonic signals that vary in frequency. For example powerful, low-frequency harmonic acoustic signals can be produced by a rapid series of gas bubble bursts from a magma conduit in volcanoes34, 35 or frictional stick-slip movement of an iceberg keel plowing through the seafloor36. The mechanism behind these volcanic and cryogenic harmonic acoustic sources is the time spacing of the pneumatic or seismic pulse series, where a variation in the Δt spacing of the pulses results in a change in the fundamental and overtone frequencies, and/or the frequency spacing between the overtones.

An example of how repeating wavelets can produce harmonic signals is shown in Fig. 3a, where a short duration pulse is repeated in series to generate a longer duration signal. A series of these wavelets (shown in inset) were then aligned using a constant inter-pulse time to construct the 15 sec long waveform, with a cosine window used to taper the signal. The fundamental frequency and overtones observed in the resulting spectrogram of the pulse-series waveform are inversely proportional to the time spacing of the maximum amplitude of the wavelet series. By varying the inter-pulse interval, Fig. 3b shows that the fundamental and overtone frequencies of the waveform are changed, while the harmonic frequency spacing remains the same.

Example waveforms and spectra demonstrating wavelet model for generating repeating pulse harmonic signals. ( a) Upper panel shows example of repeating pulse source model produced using a tapered amplitude sequence of wavelets of constant length. Upper right inset shows wavelet used (0.23 second for this demonstration). A series of these wavelets are aligned using constant inter-event time to construct the waveform below. A cosine taper is also used on the pulse series waveform. The frequency and overtones in the spectrogram of the waveform are inversely proportional to the time spacing of the maximum amplitude of the wavelets. ( b) Upper panel shows a tapered amplitude sequence of wavelets with variable inter-event time (range from 0.16-0.23 sec). Lower panel shows resulting spectrogram with shifting frequencies due to change in wavelet time length in original signal.

A detailed display of the blue whale B call from Fig. 1 is shown in Fig. 4a. This B call was recorded using a sample rate of 2 kHz, and has a fundamental frequency of 14.7 Hz with 5 overtones at 29.5, 44.2, 58.9, 73.6, and 88.4 Hz.

( a) Top panel shows small scale plot (7 sec duration) and corresponding frequency spectra of blue whale B call from Fig. 1. Note fundamental at 14.73 Hz with multiple overtones. ( b) Top panel shows repeating pulse model with source wavelet (0.18 sec duration) used to produce time series on upper right. This repeating pulse model of a blue whale B call was produced by 8000 successive wavelets and tapering the amplitude sequence. Pulse model was cross-correlated with original B call with resulting r shown.

To model this B call, we first constructed a short duration pulse P(t) using the equation:

where,

$$q(t)=1/[{(t-a)}^{2}+0.01)];\,{\rm{for}}\,{\rm{t}} < a$$

and

$$q(t)=10/[{(t-a)}^{2}+0.1)];\,{\rm{for}}\,{\rm{t}} > a$$

where a is a constant value used to set the time length of the pulse. Here we set a = 0.3 so that t > 0 and the pulse duration remains under a second. The upper right of Fig. 4b shows the 0.068 sec duration pulse wavelet produced using equation ( 1). This pulse was then repeated in series 3081 times to construct the 7 sec long B call waveform model shown in Fig. 4b.

Model comparison and acoustic propagation

To test the quality of the model fit, we cross-correlated a blue whale B call recorded on a seafloor hydrophone at 55 m depth (Fig. 4a) with the model waveform (Fig. 4b). A more detailed comparison of the observed and model call signals is also shown in Fig. 5a. The example B call presented here is a very clear signal with little high frequency noise interference. Both Figs 4 and 5 show remarkable similarities in amplitude, phase difference, pulse width and polarity between the blue whale call and the pulse model. The repeated, high amplitude phase seen in the call and in the model is the fundamental frequency of 14.73 Hz (0.068 sec time spacing, labeled with black arrows). Moreover, the resulting correlation function r of 0.93 (where a maximum correlation = 1) indicates our pulse model well matches the B call signal structure.

Three detailed records of B calls recorded by a hydrophone (dark blue) and model of B call produced using eq. 1 (light blue). Signal ( a) is from 28 September (same signal as in Fig. 1), ( b) is ~30 min after ( a), and ( c) is call recorded 6 days later. Arrows point at significant components of the actual B call signal (dark blue). Red arrows show the fundamental frequency of the B call which is the direct arrival phase (the acoustic phase with a direct path from the whale to the hydrophone). Green arrows highlight later arriving, lower amplitude signal components that include the call overtones. Time delays as well as amplitude and polarity changes are introduced into these lower amplitude signal components by propagation effects such as reflection off nearby seafloor structures (e.g. reefs, sand bars) or possibly cavities or bony structures within the whale. Signal ( a) shows best match of model to real blue call. Signals ( b) and ( c) show more mismatch in signal width, amplitude and polarity of later arriving phases possibly due to changing position and orientation of the whale relative to seafloor structures. Ocean noise levels are also much higher before and after 28 September which likely contributes to mismatch of model in ( b) and ( c).

Admittedly, by adjusting the time length of the pulse (the value of a used above), we are employing a forward modelling methodology (subjective) where source metrics are chosen that allow us to best match the model to the real signal, as opposed to discrete inverse methods that use the recorded signal to objectively derive the source parameters. We employed a forward modelling approach in this study because, while there are several physiological aspects to sound production in humpback whales that have been previously determined and modeled19, 29,30,31, the precise physical mechanism or process that produces the amplitude and pulse width of the observed blue whale B call waveforms is not fully known. Thus a forward model is our attempt to provide a new approach and different view of the B call source mechanism. The time duration of air pulses that produce blue whale B calls may be controlled by a wide variety of physiological factors that could vary between individual animals (e.g. respiratory valve thickness, tissue elasticity, strength of controlling muscles, etc). Adjusting the pulse time-decay parameter a in the model to match the observed signal is a way to account for this wide range of variables in the actual sound generation mechanism.

Closer inspection of Fig. 5a also shows the call has lower amplitude components with pulse widths and polarities that arrive between the peaks of the 14.73-Hz fundamental (highlighted with green arrows). These time-delayed, lower amplitude arrivals are also observed in B calls recorded at different times within the acoustic data set. Figure 5b and c show examples of other B calls recorded ~30 min later than the call in Fig. 5a and a call recorded 6 days later.

These lower-amplitude signal components in between the fundamentals have arrival times that do not match the expected time delay for discrete overtones. For example, the lower amplitude phases in Fig. 5a have time delays of 0.03 and 0.04 secs after the fundamental, representing 37.6 and 24.5 Hz, respectively, whereas expected overtones should be at integer multiples of the fundamental frequency; 29.5 Hz, 44.2 Hz, etc. Therefore, while these low amplitude arrivals do include the signal energy from the B call overtones, the time delays and lower amplitudes are likely caused by multipath effects from the signals reflecting/refracting off the sea-surface, seafloor and/or reef structures in this shallow water propagation environment. Moreover, because the model matches the observed B call so closely in Fig. 5a suggests the multipath effects from this particular instance are not strong, which may mean the whale was relatively close to the hydrophone at the time of this recording. In Fig. 5b,c, our model does not match the recorded B call as well, suggesting the whale was farther from the hydrophone receiver resulting in more complex propagation. Producing model estimates of the propagation paths for rays travelling from the blue whale to the hydrophone in order to map the arrival times of the various components of the B call signal structure is challenging in this shallow water environment. Since the depth of the hydrophone (~55 m) is much less than the wavelength of the B call (~100 m), a ray approximation model that yields arrival time estimates (e.g. Bellhop37), will not produce valid estimates of the multipath interference38.

However, it still seems highly likely that this mismatch in the non-fundamental components of the actual B call and the model may be due to time delays and amplitude/polarity changes due to reflections from the seafloor or nearby structures (e.g. reefs, sand bars). Evidence that these phases may be reflections comes from the observation that these components of the actual blue whale call have very different signal characteristics when recorded on different days. For example, as noted, Fig. 5a shows the best match of both fundamental and overtones with our model to an actual blue whale B call, whereas Fig. 5b and c show the same strong correlation in the fundamental frequency of the data and model, but now accompanied by a much greater degree of mismatch in signal width, amplitude and polarity for the overtones of these later arrivals. These mismatches between actual data and model might be due to variability of the real signal caused by the arrival of acoustic reflections off nearby seafloor structures as the blue whale approached, or even as the animal changed orientation or position in the water column relative to these structures. Moreover, ambient noise levels in the ocean, recorded on the hydrophones, were much higher before and after 28 September due to increased wind speeds and sea-surface wave heights. Ambient ocean noise generated by wind and surface waves is known to be broadband centered at 200 Hz39 but can go as low as <10 Hz40, even in shallow water. We think it is also possible that the discrepancies between the model and observed calls in Fig. 5b,c may be due to relatively high background noise levels, which will be present in the observed signal despite filtering because the noise and the whale call occur in the same frequency band

The non-fundamental signal components may also result, in part, because the blue whale is not a "perfect" signal generator. The waveforms produced by any natural system will have internal reflections from anatomical structures and/or cavities within the animal itself. These ancillary sound sources from within the animal can be further complicated by acoustic propagation effects within the water-column. Although, as noted by Reidenberg and Laitman19, once the sound is generated inside the animal the signal is likely not distorted much by propagation through the animal's tissues and throat pleats, since the density of the tissues and pleats is closer to the density of sea water than air.

If high-resolution bathymetry were to be collected in the vicinity of the hydrophone, it might be possible to identify seafloor structures that act as these acoustic reflectors. However, without the exact three-dimensional path of the blue whale through the water-column, it is not possible to precisely calculate the propagation path and arrival time of these reflections in order to identify these phases in the B call signals.

Comparison to Resonance Based Source Model

Previous models of blue whale calls have been based on either summation of sinusoids41, 42 or Gaussian curves43. A key distinction between our pulse model and previous sinusoidal/Gaussian models is that the latter is characteristic of a resonance source mechanism. To compare the match between our pulse and resonance-based models, a sinusoidal based blue B call model is shown in Fig. 6. The model developed by Mellinger et al.41, is a sine function summation but with a variable phase term introduced to better improve the match of the width of the model individual waveforms. This model dynamically changes the amplitude and frequency in the waveform, and is the basis for animal and non-animal signal detection algorithm that tracks the spectral peaks of the call frequencies over time. The algorithm function SP is given by:

$${\rm{SP}}={\sum }_{(i=0)}^{(N-2)}[{{\rm{A}}}_{0}+i({{\rm{A}}}_{1}-{{\rm{A}}}_{0}){({\rm{N}}-1)}^{-1}]\sin ({\rm{P}}+2\pi {{\rm{R}}}^{-1}\,[{\sum }_{j=0}^{i}j({{\rm{F}}}_{1}-{{\rm{F}}}_{0})/{\rm{N}}+{{\rm{F}}}_{0}])$$

where R is the sample rate, P is the phase (here set to 0), and N is the number of data points (product of R and the duration in seconds). Also F ₀ and F ₁ are the observed fundamental and overtones frequencies (in this case 14.73, 29.5 Hz) but varied at ±0.42 Hz, respectively, to simulate the slight frequency sweep of the tones. The values for A ₀ and A ₁ are the amplitude coefficients used to keep the signal range between ±1.5 and to adjust for variation in signal amplitude.

Example of a sinusoidal based blue whale B call model. The model here is a sine function summation, but with a variable phase term introduced (eq. 3) to better improve the match of the width of individual waveforms38. The model was cross-correlated with an original B call, and resulting r is shown.

As with the pulse model (eq. 1), this sine-based algorithm (eq. 2) was cross-correlated to the actual B call signal to gauge the accuracy of the model fit. Correlation of the function in eq. 2 with the B call in Fig. 6 results in a r value of 0.87, indicating a good match of this model to the actual call. However, the pulse series model (eq. 1) still appears to do the best job of simulating the B call, as indicated by the higher correlation r value of 0.93, which lends support to our hypothesis that a series of air pulses may likely involved in the formation of a blue whale B call. Nevertheless, the high correlation of the sinusoid phase delay model (eq. 2) indicates that internal resonance within the animal may also contribute to generation of the B call.

Discussion

We suggest that blue whales produce B calls by rapid opening and closing of one of their respiratory valves, which yields a series of pneumatic air bursts or pulses. This opening and closing of respiratory valves is likely passively triggered by the physical interaction of airflow (through lungs and upper respiratory structures) and U-fold tissues, i.e. the self-oscillating flow-induced vocal production model proposed by Cazau et al.29, 31 for humpback whales. These pneumatic bursts, taken in series, produce the fundamental and overtone frequencies of the B call. This signal process is demonstrated by the models shown in Figs 3 and 4, where the frequency and overtones of the B call are inversely proportional to the time spacing of the maximum amplitude of the pneumatic pulses. Moreover, any variation in this inter-pulse time spacing will result in a shift of the fundamental and overtone frequencies through time that also maintains the frequency spacing between the overtones. Thus similar to previous models for humpbacks29, 31, the pulse model described here also allows for changes in frequency of the B call through time as observed in actual calls.

We further suggest that these pneumatic air pulses can be produced, as outlined in Cazau et al.29 for humpback whales, by one of three physiological configurations for the laryngeal respiratory valves. In our view, the main source of the pneumatic pulses is likely from repeated rapid adduction and dorsal elevation of the U-fold vocal process against the cricoid cartilage, causing pulsed (restriction and release) airflow from the trachea into the laryngeal sac and upper respiratory structures19, 30. This adduction is likely passively driven by airflow as is thought to be the case for humpbacks29. However, the corniculate cartilage and the epiglottis are also respiratory valves and will open and close in association, and in various configurations, with the U-fold29. Thus all three valves may take turns being either the main valve controlling the rate and duration of the pneumatic air bursts, or may coordinate with the other vales in controlling the pulse of air. In addition, the U-fold edges and laryngeal sac walls may also vibrate and resonate with airflow, potentially amplifying these pulse signals19. Frequency modulation of the air pulses may also result from the inflation of the laryngeal sac, stretching in correspondence the U-fold through the particular free-floating attachment between its lumen and the arytenoid muscle, instead of being produced through the activity of dedicated laryngeal muscles19, 29. Pulsed inflation of the laryngeal sac may also cause pulsed distention of ventral throat grooves, facilitating sound transfer into the water19. While our pulse model implies that harmonic sounds of blue whales are primarily produced by pneumatic airflow through the respiratory valves, the laryngeal sac and nasal passages likely ﻿still﻿ produce resonance sound during airflow, adding to the overall B call energy and structure, and/or contributing to the generation of observed secondary pulses.

The pulse series model also implies that the whale can change the frequency of the B call while the call is being created, which may account for several examples of unusual B calls previously observed. For example, Stafford and Moore44 showed the existence of an atypical B call series recorded from blue whales in the north Pacific. The unusual B call pattern consisted of an abrupt rise in frequency within the call. Stafford and Moore44 attributed this unusual record to either an individual producing a hybrid song that included both northeastern and northwestern blue whale call units and/or two individuals from either population vocalizing in perfect synchrony with each other. Although we cannot rule out two individuals vocalizing, the unusually rapid change in call frequency could be due to a blue whale cognitively changing the time between pneumatic air pulses and, therefore, changing the frequency within the call. Similarly, Thode et al.22 showed examples of Channel Island blue whale B calls that had unusual U-shaped frequency modulation in addition to the well-established down-sweep. Thode et al.22 attributed these call structures to mechanical resonance within the animal, but noted the vocalizing-depth to frequency-shift relationship does not fit any simple air-filled Helmholtz resonator model.

Beginning in the early 1990s, a unique series of whale calls were observed centered at 52 Hz, ~6 sec in duration, with no under- or overtones44, 45. Watkins et al.45 attributed this to an unknown large whale species, while Stafford and Moore41 observed that the call shared characteristics with the third harmonic of eastern north Pacific blue whale B calls and therefore may be part blue whale or perhaps a blue-fin hybrid. It is not uncommon to observe northeastern Pacific blue whale call series where the fundamental and first overtone of the B call are not recorded and only the third harmonic of the call is observed44. A simple resonating source model cannot account for removal of fundamental tone energy, and still allow high energy production of the high overtone. The pulse model presented here provides a physical mechanism, as does the Cazau et al.29, 31 model for vocal production in humpback whales, whereby call frequencies could be actively changed by the animal to center fundamental tones at different frequency bands during the call series.

McDonald and Hildebrand3 observed that northeastern Pacific blue whale songs, measured at the fundamental frequency and third harmonic, have been exhibiting a long-term linear downward trend and are now 31% lower in frequency than they were in the 1960s. They suggest this downward shift is related to increased population size post commercial whaling, modified by trade-offs between short- and long-distance communication and global ambient noise increases due to shipping. A similar long-term decrease in vocalization frequencies of both Antarctic blue and eastern Indian Ocean pygmy blue whales has also been observed15, 46. We speculate that our pulse model may provide a viable mechanism to account for this observed change in frequency whereby blue whales are able to cognitively lower their call frequency to adjust for long term changes in the ocean soundscape and their environment.

Despite the difference in physical mechanisms between a purely resonance and pulse model of sound production in blue whales, the previously proposed limits on a whale's B call structure and pattern imposed by maximum dive depth, inhalation, and feeding would still apply18. Global observations of tonal blue whale calls show sound level intensity of these calls is relatively constant over the duration of the call, indicating there is a near constant air flow rate from the lungs across the respiratory valves during the call production. Moreover, it might take less energy for the whale to vocalize during dive or ascent because the change in hydrostatic pressure may facilitate the flow of air from and/or into the lungs across the respiratory valves, allowing the animal to maintain the sound intensity over the typical time duration of B calls (~10-20 sec). Assumptions of lung and laryngeal sac volumes imply sound production at a maximum dive depth limit of <200 m3, 18, although models of airflow rates show vocalization depths may range from 0-90 m, consistent with observed vocalization depths of 10-40 m22. Thus these depth limits and differential pressure restrictions are still applicable to our proposed pulse model because the model is based on the whale's ability to maintain a high airflow rate across the oscillating, respiratory valves.

While the pulse model presented here is still in the preliminary stages of development, our first-order analysis indicates the model may provide an alternative mechanism to explain unusual blue whale call characteristics that cannot be fully explained by resonance of air-filled organs within the animal. The pulse model may also be applied to vocalizations of other baleen whale species or marine animals to help understand how oddly-low frequency vocalizations can be produced by animals of small body size. For example, even though Atlantic cod ( Gadus morhua) are typically <1 m in body length, they produce low frequency harmonic spawning sounds in the 50-150 Hz range49. These frequencies require sound wavelengths, as well as a resonating source dimension, on the order of 10-30 m. Hence an internal pneumatic pulsed air mechanism may help explain the low frequency vocalization characteristics of these animals.

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Acknowledgements

We wish to thank J Zeeman and Gigantic Pictures for initial financial support for this project, and K. Stafford for very helpful reviews of the manuscript and J. Hildebrand for insights into resonance and proper application of our model. We wish to thank the three anonymous reviewers for their helpful comments and suggested edits that greatly improved the manuscript. We also thank D. Bohnenstiehl for graciously providing Figure 3. This research was additionally supported by the NOAA/PMEL Acoustics Program. This paper is PMEL contribution number 4430.

Author information

Authors and Affiliations

1. NOAA/Pacific Marine Environmental Laboratory, Newport, OR, 97365, USA

R. P. Dziak

2. Cooperative Institute for Marine Science Studies, Oregon State University/NOAA, Hatfield Marine Science Center, Newport, OR, 97365, USA

J. H. Haxel, T.-K. Lau, S. Heimlich, D. K. Mellinger & H. Matsumoto

3. Department of Geology, Western Washington University, Bellingham, WA, 98225, USA

J. Caplan-Auerbach

4. Marine Mammal Institute, Oregon State University Hatfield Marine Science Center, Newport, OR, 97365, USA

B. Mate

Contributions

R. Dziak developed the original mathematical model, wrote the paper, and produced several of the figures. J. Haxel collected the hydrophone data, produced Figure 1, and co-authored the paper. T-K Lau assisted in developing mathematical model, produced software code of blue B call model and generated Figures 4 and 6. S. Heimlich performed original data analysis, contributed on Figures 2 and 5 and edited manuscript. J. Caplan-Auerbach tested acoustic propagation models and edited manuscript. D. Mellinger assisted in application of equation 3 and development of model in Figure 6. H. Matsumoto assisted in development of call model and interpretation acoustic propagation model. B. Mate initiated project to review and analyze northeast Pacific blue whale calls on our hydrophone data.

Corresponding author

Correspondence to R. P. Dziak.

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Dziak, R.P., Haxel, J.H., Lau, TK. et al. A pulsed-air model of blue whale B call vocalizations. Sci Rep 7, 9122 (2017). https://doi.org/10.1038/s41598-017-09423-7
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# data[].attributes.attachment_link.title
A pulsed-air model of blue whale B call vocalizations - Scientific Reports

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Blue whale sound production has been thought to occur by Helmholtz resonance via air flowing from the lungs into the upper respiratory spaces. This implies that the frequency of blue whale vocalizations might be directly proportional to the size of their sound-producing organs.

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Anthropogenic Noise impairs cooperation between dolphins

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Anthropogenic Noise impairs cooperation between dolphins

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Peter Tyack, St Andrews

Sørensen, PM, Haddock, A, Guarino, E, Jaakkola, K, McMullen, C, Jensen, FH, Tyack, PL & King, SL 2023, 'Anthropogenic noise impairs cooperation in bottlenose dolphins', Current Biology, vol. 33, no. 4, pp. 749-754. https://doi.org/10.1016/j.cub.2022.12.063

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Anthropogenic noise impairs cooperation in bottlenose dolphins

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Star burst: a solar flare as seen by NASA's Solar Dynamics Observatory. (Courtesy: NASA/SDO)

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Marko proposed this. Need to investigate.

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In mysticetes and sirenians, the earbones have bony connections to the skull. The exact mechanism that mysticetes use for hearing is still being researched.

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In mysticetes and sirenians, the earbones have bony connections to the skull. The exact mechanism that mysticetes use for hearing is still being researched.

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Racicot, Rachel A., Robert W. Boessenecker, Simon A. F. Darroch, and Jonathan H. Geisler. "Evidence for Convergent Evolution of Ultrasonic Hearing in Toothed Whales (Cetacea: Odontoceti)." Biology Letters 15, no. 5 (2019/05/15 2019): 20190083. https://doi.org/10.1098/rsbl.2019.0083. https://doi.org/10.1098/rsbl.2019.0083.

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With latin names:

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chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://dl.acm.org/doi/pdf/10.1145/2502081.2502125

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Comparison table: human Vs. cetacean hearing

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Comparison table: human Vs. cetacean hearing

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Dosits website

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Paper by Marko et al. Whale Watching apps

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Paper by Marko et al. Whale Watching apps

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From below 0.2 hz to 30 hz - but the higher frequencies attenuate quickly so won’t be perceptible away from the epicentre or (I’m guessing) in secondary waves.

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Seismic waves are waves of energy that travel through the Earth's layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy. Many other natural and anthropogenic sources create low-amplitude waves commonly referred to as ambient vibrations. Seismic waves are studied by geophysicists called seismologists. Seismic wave fields are recorded by a seismometer, hydrophone (in water), or accelerometer.

The propagation velocity of seismic waves depends on density and elasticity of the medium as well as the type of wave. Velocity tends to increase with depth through Earth's crust and mantle, but drops sharply going from the mantle to the outer core.

Earthquakes create distinct types of waves with different velocities; when reaching seismic observatories, their different travel times help scientists to locate the source of the hypocenter. In geophysics the refraction or reflection of seismic waves is used for research into the structure of the Earth's interior, and man-made vibrations are often generated to investigate shallow, subsurface structures.

Among the many types of seismic waves, one can make a broad distinction between body waves, which travel through the Earth, and surface waves, which travel at the Earth's surface.

Other modes of wave propagation exist than those described in this article; though of comparatively minor importance for earth-borne waves, they are important in the case of asteroseismology.

Body waves travel through the interior of the Earth.

Surface waves travel across the surface. Surface waves decay more slowly with distance than body waves, which travel in three dimensions.

Particle motion of surface waves is larger than that of body waves, so surface waves tend to cause more damage.

Body waves travel through the interior of the Earth along paths controlled by the material properties in terms of density and modulus (stiffness). The density and modulus, in turn, vary according to temperature, composition, and material phase. This effect resembles the refraction of light waves. Two types of particle motion result in two types of body waves: Primary and Secondary waves.

Primary waves (P-waves) are compressional waves that are longitudinal in nature. P-waves are pressure waves that travel faster than other waves through the earth to arrive at seismograph stations first, hence the name "Primary". These waves can travel through any type of material, including fluids, and can travel nearly 1.7 times faster than the S-waves. In air, they take the form of sound waves, hence they travel at the speed of sound. Typical speeds are 330 m/s in air, 1450 m/s in water and about 5000 m/s in granite.

Secondary waves (S-waves) are shear waves that are transverse in nature. Following an earthquake event, S-waves arrive at seismograph stations after the faster-moving P-waves and displace the ground perpendicular to the direction of propagation. Depending on the propagational direction, the wave can take on different surface characteristics; for example, in the case of horizontally polarized S waves, the ground moves alternately to one side and then the other. S-waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses. S-waves are slower than P-waves, and speeds are typically around 60% of that of P-waves in any given material. Shear waves can't travel through any liquid medium, so the absence of S-wave in earth's outer core suggests a liquid state.

Surface waves

Seismic surface waves travel along the Earth's surface. They can be classified as a form of mechanical surface waves. They are called surface waves, as they diminish as they get further from the surface. They travel more slowly than seismic body waves (P and S). In large earthquakes, surface waves can have an amplitude of several centimeters.

Rayleigh waves, also called ground roll, are surface waves that travel as ripples with motions that are similar to those of waves on the surface of water (note, however, that the associated particle motion at shallow depths is retrograde, and that the restoring force in Rayleigh and in other seismic waves is elastic, not gravitational as for water waves). The existence of these waves was predicted by John William Strutt, Lord Rayleigh, in 1885. They are slower than body waves, roughly 90% of the velocity of S waves for typical homogeneous elastic media. In a layered medium (like the crust and upper mantle) the velocity of the Rayleigh waves depends on their frequency and wavelength. See also Lamb waves.

Love waves are horizontally polarized shear waves (SH waves), existing only in the presence of a semi-infinite medium overlain by an upper layer of finite thickness. They are named after A.E.H. Love, a British mathematician who created a mathematical model of the waves in 1911. They usually travel slightly faster than Rayleigh waves, about 90% of the S wave velocity, and have the largest amplitude.

A Stoneley wave is a type of boundary wave (or interface wave) that propagates along a solid-fluid boundary or, under specific conditions, also along a solid-solid boundary. Amplitudes of Stoneley waves have their maximum values at the boundary between the two contacting media and decay exponentially towards the depth of each of them. These waves can be generated along the walls of a fluid-filled borehole, being an important source of coherent noise in VSPs and making up the low frequency component of the source in sonic logging. The equation for Stoneley waves was first given by Dr. Robert Stoneley (1894-1976), Emeritus Professor of Seismology, Cambridge.

Free oscillations of the Earth are standing waves, the result of interference between two surface waves traveling in opposite directions. Interference of Rayleigh waves results in spheroidal oscillation S while interference of Love waves gives toroidal oscillation T. The modes of oscillations are specified by three numbers, e.g., nS l m, where l is the angular order number (or spherical harmonic degree, see Spherical harmonics for more details). The number m is the azimuthal order number. It may take on 2 l+1 values from - l to + l. The number n is the radial order number. It means the wave with n zero crossings in radius. For spherically symmetric Earth the period for given n and l does not depend on m.

Some examples of spheroidal oscillations are the "breathing" mode ₀S ₀, which involves an expansion and contraction of the whole Earth, and has a period of about 20 minutes; and the "rugby" mode ₀S ₂, which involves expansions along two alternating directions, and has a period of about 54 minutes. The mode ₀S ₁ does not exist because it would require a change in the center of gravity, which would require an external force.

Of the fundamental toroidal modes, ₀T ₁ represents changes in Earth's rotation rate; although this occurs, it is much too slow to be useful in seismology. The mode ₀T ₂ describes a twisting of the northern and southern hemispheres relative to each other; it has a period of about 44 minutes.

The first observations of free oscillations of the Earth were done during the great 1960 earthquake in Chile. Presently periods of thousands of modes are known. These data are used for determining some large scale structures of the Earth interior.

P and S waves in Earth's mantle and core

When an earthquake occurs, seismographs near the epicenter are able to record both P and S waves, but those at a greater distance no longer detect the high frequencies of the first S wave. Since shear waves cannot pass through liquids, this phenomenon was original evidence for the now well-established observation that the Earth has a liquid outer core, as demonstrated by Richard Dixon Oldham. This kind of observation has also been used to argue, by seismic testing, that the Moon has a solid core, although recent geodetic studies suggest the core is still molten[citation needed ].

The path that a wave takes between the focus and the observation point is often drawn as a ray diagram. An example of this is shown in a figure above. When reflections are taken into account there are an infinite number of paths that a wave can take. Each path is denoted by a set of letters that describe the trajectory and phase through the Earth. In general an upper case denotes a transmitted wave and a lower case denotes a reflected wave. The two exceptions to this seem to be "g" and "n".

c

the wave reflects off the outer core

d

a wave that has been reflected off a discontinuity at depth d

g

a wave that only travels through the crust

i

a wave that reflects off the inner core

I

a P-wave in the inner core

h

a reflection off a discontinuity in the inner core

J

an S wave in the inner core

K

a P-wave in the outer core

L

a Love wave sometimes called LT-Wave (Both caps, while an Lt is different)

n

a wave that travels along the boundary between the crust and mantle

p

a P wave ascending to the surface from the focus

s

an S wave ascending to the surface from the focus

w

the wave reflects off the bottom of the ocean

No letter is used when the wave reflects off of the surfaces

For example:

ScP is a wave that begins traveling towards the center of the Earth as an S wave. Upon reaching the outer core the wave reflects as a P wave.

sPKIKP is a wave path that begins traveling towards the surface as an S-wave. At the surface it reflects as a P-wave. The P-wave then travels through the outer core, the inner core, the outer core, and the mantle.

In the case of local or nearby earthquakes, the difference in the arrival times of the P and S waves can be used to determine the distance to the event. In the case of earthquakes that have occurred at global distances, three or more geographically diverse observing stations (using a common clock) recording P-wave arrivals permits the computation of a unique time and location on the planet for the event. Typically, dozens or even hundreds of P-wave arrivals are used to calculate hypocenters. The misfit generated by a hypocenter calculation is known as "the residual". Residuals of 0.5 second or less are typical for distant events, residuals of 0.1-0.2 s typical for local events, meaning most reported P arrivals fit the computed hypocenter that well. Typically a location program will start by assuming the event occurred at a depth of about 33 km; then it minimizes the residual by adjusting depth. Most events occur at depths shallower than about 40 km, but some occur as deep as 700 km.

A quick way to determine the distance from a location to the origin of a seismic wave less than 200 km away is to take the difference in arrival time of the P wave and the S wave in seconds and multiply by 8 kilometers per second. Modern seismic arrays use more complicated earthquake location techniques.

At teleseismic distances, the first arriving P waves have necessarily travelled deep into the mantle, and perhaps have even refracted into the outer core of the planet, before travelling back up to the Earth's surface where the seismographic stations are located. The waves travel more quickly than if they had traveled in a straight line from the earthquake. This is due to the appreciably increased velocities within the planet, and is termed Huygens' Principle. Density in the planet increases with depth, which would slow the waves, but the modulus of the rock increases much more, so deeper means faster. Therefore, a longer route can take a shorter time.

The travel time must be calculated very accurately in order to compute a precise hypocenter. Since P waves move at many kilometers per second, being off on travel-time calculation by even a half second can mean an error of many kilometers in terms of distance. In practice, P arrivals from many stations are used and the errors cancel out, so the computed epicenter is likely to be quite accurate, on the order of 10-50 km or so around the world. Dense arrays of nearby sensors such as those that exist in California can provide accuracy of roughly a kilometer, and much greater accuracy is possible when timing is measured directly by cross-correlation of seismogram waveforms.

Shearer, Peter M. (2009). Introduction to Seismology. Cambridge University Press. ISBN 978-0-521-88210-1.

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Seismic waves are waves of energy that travel through the Earth's layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy. Many other natural and anthropogenic sources create low-amplitude waves commonly referred to as ambient vibrations.

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https://onlinelibrary.wiley.com/doi/pdf/10.1111/maec.12499

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https://savethewhales.org/education/#:~:text=ODONTOCETES%20(toothed)%20and%20MYSTICETES%20(,mysticetes%20have%20two%20external%20blowholes.

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When we think of whales, the enormous ones that filter tiny plankton from seawater with their baleen-fringed upper jaw often come first to mind (like the right whale in the picture above). But cetaceans also include dolphins, porpoises and other toothed whales, and in total contain more than 80 different species.

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Conference in Barcelona 2024. Decade runs from 2021 to 30. RCA is a partner, but seems design focused.

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Three years after the start of the UN Decade of Ocean Science for Sustainable Development (2021-2030), a global conference will bring together the Ocean Decade community and partners to celebrate achievements and set joint priorities for the future of the Decade. Hosted by Spain and co-orga…

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Auditory response to electromagnetic waves

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Auditory response to electromagnetic waves

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Testing lower frequency sampling's effectiveness in recording dolphin clicks

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Testing lower frequency sampling's effectiveness in recording dolphin clicks

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"Therefore, despite reaching high frequencies, the clicks can also be recorded at lower frequencies because echolocation clicks from bottlenose dolphins are broadband. We concluded that ecological studies based on the presence–absence data are still effective for bottlenose dolphins when acoustic devices with a limited sampling rate are used." Abstract

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Denon Professional - Professional-grade Audio/Video Recording, Playback and Signal Distribution

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Leaders in professional-grade audio/video recording, playback and signal distribution. Delivering premium products for the recording, playback and management of multimedia signal sources, Denon Professional is trusted by the most demanding professional installers and system integrators around the wo…

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Understanding sample rates and Audio sampling

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Understanding sample rates and Audio sampling

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When you're trying to sample audio from an analogue source, a calculation takes place inside the computer. The calculation converts the analogue sounds of a guitar, keyboard or other instrument into digital data. Sample rate is key to the quality of this conversion.

In this article we'll look at how sample rates affect the quality of your digital audio and explore the role of bit depth. We'll also show you how to convert and compress the final product so it can be manipulated and moved easily.

What you'll learn:

What are sample rates?

Audio sampling is the process of transforming a musical source into a digital file. Digital audio recording does this by taking samples of the audio source along the soundwaves at regular intervals. The more samples you take - known as the 'sample rate' - the more closely the final digital file will resemble the original. A higher sample rate tends to deliver a better-quality audio reproduction.

Sample rates are usually measured per second, using kilohertz (kHz) or cycles per second. CDs are usually recorded at 44.1kHz - which means that every second, 44,100 samples were taken.

If you can master sample rates, you can create more accurate recordings. Once you have this digital copy you can manipulate, mix and edit without losing any sound quality.

The final sound quality of your recording relies on more than just sample rate - bit depth also plays its part.

What is bit depth/rate?

Every sample you take when making an audio recording needs to be stored within your computer's 'bits'. The more bits you use to record each sample, the better the sound reproduction.

In other words, a high sample rate along with a high bit depth (AKA 'bit rate' or 'sample format') will deliver the best audio quality in your recording. The higher the bit depth, the higher the dynamic range.

Dynamic range is the difference between the low volume and high volume sections of your recording. This is measured in decibels - or dBs. The human ear can hear sounds up to 90dB, but recording over this level allows softer sounds to be amplified for high fidelity audio.

8-bit audio.

This is a fairly low-quality reproduction, producing audio at 46dB - around half the top level of human hearing.

16-bit audio.

This is where the human ear can usually hear to at 96dB.

24-bit audio.

While at 145dB it's well above the human hearing range, it can be useful to work at this level to reduce the 'noise floor' - essentially the digital white noise.

32-bit float audio.

This can offer nearly infinite decibel levels and is really only used for super-high-quality audio - for example, sudden loud noises that need capturing without the use of limiters.

Why is the standard audio sample rate 44.1kHz?

Many modern-day recordings use the 44.1kHz sample rate and it's the standard rate for CDs. This is partly down to how sample rates work and how we hear as humans.

Sample rates were first discussed in the 1940s, as part of the Nyquist-Shannon theorem. This states that any sampling rate must have twice the frequency of the original recording, otherwise the sound is not faithfully reproduced.

The human ear can hear between 20 hertz (20Hz) and 20 kilohertz (20kHz). 44.1kHz is more than twice the top range of human hearing, so will provide a very accurate reproduction according to the theory.

Some people still record in higher sample rates to capture all sounds. While we can't hear these in the original recordings, if an audio sample recorded at 192kHz was pitched down, some hitherto inaudible frequencies would become audible. If it was recorded at a lower sample rate and then pitched down, some of the highs in that audio would be lost.

However, even if you're recording at a higher rate, it will be likely converted back to 44.1kHz - the rate to which many modern audio systems are set.

What other sample rates are used - and what for?

With 44.1kHz the standard for CD audio, you might wonder why other sample rates exist. As we've mentioned, higher sampling rates can provide clearer audio with no white noise. They can also be useful for mastering and mixing audio. Even if we can't hear some sounds, they do exist in the higher sampling rate recording and so can still be manipulated.

48kHz.

This sample rate is also used as a standard rate alongside 44.1kHz. Do check though, as audio recorded in one rate and played at another will be either speeded up or slowed down.

88.2kHz.

This is now the gold standard for hi-res recordings. Using this sample rate produces less distortion (called 'aliasing') when converting from analogue to digital and allows greater freedom when mixing and mastering.

96kHz.

Similar to 88.2kHz, this sample rate provides more options when mixing and mastering the audio. But working at these higher rates could be an issue if your computer can't handle the added information and storage needed.

192kHz.

Some reports have suggested that recording at such a high sample rate can produce issues in your audio, such as jittering. It's also hard to find computers that can handle it. Really, it's only useful for slowing down high-frequency audio.

Can I compress an audio file without losing quality?

When dealing with high sample rates, you're going to end up with large files. To get a rough idea of how big a file is going to be, you can use these calculations:

Sample rate (in hertz not kilohertz) x Bit rate x Number of channels x Number of seconds = total bits

Bytes/1,000,000 = megabytes or MBs

44100Hz x 16-bit x 2 channels for stereo recording x 4400 seconds (a 74-minute CD recording) = 6,209,280,000 bits - or around 6.2billion bits

6,209,280,000 bits/8 = 776,160,000 bytes or 776 million bytes

776,160,000 bytes/1,000,000 = 776.16 MB

Compressing the file size.

Transferring and working with files this size can be difficult. One option is to compress the file size.

Compressing audio has been common practice since the launch of MP3 files. Such files allowed audio to be compressed with little impact on its quality. Converting audio to MP3 - which can be done on many computers and some websites - can reduce file size by a factor of 10 in some cases. It does this by removing any recorded audio that the human ear can't pick up.

To compress your audio file with Adobe Audition, simply select the MP3 file format when saving. It's important that you only compress to MP3 once, otherwise a file risks being recompressed. This can make any artefacts - or sonic errors - more pronounced.

MP3s are either compressed to 128 kbps or, more common recently, 256 kbps and 320 kbps. This is referred to a 'lossy' compression, where there is some actual loss in sound quality - even if most people can't hear it.

Lossless compression.

Alternatively, there is a lossless compression. This reduces file size without losing any sound quality. Instead of removing audio, it rewrites data in the file in a more efficient manner. These file sizes are larger than MP3s - usually cutting the file size in half, instead of reducing it to a tenth of the original.

These types of files are generally not used for daily use, but more as a way to store audio. The main types are FLAC, WavPack, Monkey's Audio and ALAC (Apple Lossless).

How to convert an audio file to a different sample rate in Adobe Audition.

You can easily convert an audio file into a different sample rate using Adobe Audition.

First, check what sample rate the sound card on your computer supports, as these can be limited. Then follow these steps:

1. Click Waveform Editor > Edit > Convert Sample Type - or simply double-click the Sample Type section of the status bar

2. Select the new rate you want from Sample Rate list or enter a customised rate in the text box

3. Click Advanced then drag the Quality Slider to adjust the quality of the sampling conversion

4. Select Pre/Post Filter to prevent distortion/aliasing noise

Discover the full range of audio sample, mixing and mastering features available with Adobe Audition.

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Sample Rates and Audio Sampling: A Guide for Beginners | Adobe

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When you're trying to sample audio from an analogue source, a calculation takes place inside the computer. The calculation converts the analogue sounds of a guitar, keyboard or other instrument into digital data. Sample rate is key to the quality of this conversion.

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We are all familiar with the two digital audio file descriptors sample rate and , and though these specifications seem routine I often get questions from producers and engineers about the optimum settings for a given project. This article covers the basics and best practices for setting sample rates. In another article, we cover the ins and outs of bit depth.

Sample Rate Defined

Sample rate defines how many times per second we sample, or take a measurement of, an analog audio signal as it is converted into a digital signal. The sample rate also defines the high- frequency response of an audio recording. The Nyquist Theorem states that the highest audio frequency we can record is half of the frequency of the sampling rate. This means that with a sample rate of 44.1 kHz, we can record audio signals up to 22.05 kHz. Likewise, a 96 kHz sample rate allows for 48 kHz of audio bandwidth.

If we attempt to record audio frequencies above half the sample rate (also called the Nyquist Frequency), audible artifacts called aliasing can occur. Audio-frequency aliasing is much like the wagon-wheel effect seen in videos. When we film a wheel with spokes that starts to spin and its rotational speed increases, it begins to look like it slows and then spins backward. This effect happens when the wheel's speed approaches the frame rate of the video. Audio aliases are frequencies that are reflected below the Nyquist frequency and sound like strange non-musical harmonics.

Analog to digital converters can apply a low-pass filter before sampling so that no audio above the Nyquist frequency enters the A-D converter. This low-pass filter is referred to as an anti-aliasing filter. Unfortunately, low-pass filters have some side effects. If we apply a gentle low-pass filter to eliminate everything above, say 22 kHz, we will also slightly reduce the level of audio as much as an octave below 22 kHz, or 11 kHz. To avoid that, we could use a very steep low-pass filter, but steep filters create audible artifacts like ringing or phase shifts. Most modern A-D converters and interfaces actually sample at a very high sample rate and then downsample to the chosen sample rate to avoid the problems created by analog low-pass filters. The important thing to remember is that your system won't record audio frequencies above half of the sample rate.

We know that human hearing reaches from about 20Hz to 20 kHz, so why would we need sampling rates above 44.1 kHz? One answer is that many people, including scientists, claim that humans can perceive sounds as high as 50 kHz through bone conduction. That claim may theoretically be correct, but through air humans only hear up to about 20 kHz, so in a perfect world 20 kHz would be all the frequency range needed by humans. A more practical reason for different sample rates is that Interfaces, A-D converters, and even plugins may sound different at different sample rates, depending on their architecture and how they deal with aliasing.

For example, plugins like limiters can create new high harmonics ( distortion) that reach above the Nyquist Frequency and could cause additional audible distortions or colorations, so many plugins internally oversample the audio, or process the audio at multiple of the session's sample rate so that any new high-frequency content does not create aliasing. The plugins then filter out the unwanted high frequencies and reduce the processed audio back to the original sample rate. Oversampling comes at the expense of CPU power and latency but can produce less colored processing. Next time you put a maximizer on your mix, audition the plugin with and without oversampling turned on to see if you hear a difference. Some processors do not allow the user to choose the oversampling and we just have to listen carefully to decide if we like the resulting audio. Oversampling is especially important for plugins like compressors, limiters, saturators, and exciters which inherently create harmonic distortion.

Standard Sample Rates

I have surveyed many professional producers, mixers, and mastering engineers, and most commercial top-40 records are recorded, mixed, and mastered at 44.1 kHz or 48 kHz. Professional studios use high-quality converters which sound great at all sample rates and the main reason to stick to 44.1 or 48 kHz sampling is simply to conserve CPU power when mixing and processing. Many pop songs contain hundreds of audio tracks and high sample rates could limit the ability to use CPU-intensive plugins. Music distributed on CD is 44.1 kHz while music embedded in video is usually 48 kHz, so both formats are popular and completely acceptable.

High Sampling Rates

For audiophile recordings and sound design projects, I recommend the 96 kHz sample rate, mainly for practical reasons. First, this sample rate eliminates audible high-frequency aliasing and filter-induced distortions from A-D conversion and plugins and avoids the user having to decide when to turn on oversampling. Second, it may be surprising to learn that 96 kHz audio files also provide lower processing latency. Plugin latency is based on a certain number of samples regardless of sample rate, so at higher sample rates a given number of samples goes by quicker than at lower sample rates. This is why digital consoles for live sound often operate at 96 kHz.

As an added benefit to sound designers, 96 kHz allows audio to be pitch-shifted an octave down and still retain some high-frequency content-provided your mic and recording chain can capture up to at least 40 kHz. Imagine recording a sword fight for a video game or movie and pitch-shifting the metallic sounds down to a lower frequency to exaggerate their impact. If you were limited to 22 kHz audio (44.1 kHz sample rate) and shifted the recording down by an octave, there would be no audio left above about 10 kHz, so the pitch-shifted audio may sound dull or filtered.

Best Practices for Sample Rate

If you feel the need to record at sample rates above 96 kHz, you should spend a considerable amount of time auditioning your converters, DAW, and plugins to find a workflow that suits your purpose. Sample rates at or above 96 kHz will tax your CPU, may reduce your track count, and provide fewer plugin choices. I would generally recommend against working at 176 kHz or 192 kHz unless you have truly studied the pros and cons of those high sampling rates. For reference, the Grammy's Recording Academy Recommendations for Hi-Resolution Music Production document proposes a minimum sample rate of 48 kHz and a preferred sample rate of 96 kHz for hi-res audio production and delivery.

Surprisingly, some well-regarded plugins only process audio up to 48 kHz, so in a session with a higher sample rate, any audio passed through these plugins will result in the audio's frequency response being reduced. If you wish to work at sample rates of 96 kHz or higher, check with your favorite plugin manufacturers to see if they report any limitations.

Sample Rate Conversion

Sometimes sample rate conversion is unavoidable and many software utilities provide excellent sample rate conversion. From a recent survey of mastering engineers, here are some recommended sample rate conversion programs: Voxengo r8brain, Weiss Saracon, Pro Tools SRC (using its TweakHead settings), Izotope RX10 Resample, and the command line utility SoX. Many other programs provide excellent results and DAWs are continually improving their SRC algorithms.

Keep these issues in mind and choosing the best sample rate for your project shouldn't be too difficult. Here is a cheat sheet to help keep it all organized:

Continue reading other tips and tricks on our blog.

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Understanding Sample Rate - Sonarworks Blog

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This article covers what the sample rate is and the basics and best practices for setting sample rates. Sample Rate Cheat Sheet included!

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Another example of waves with both longitudinal and transverse motion may be found in solids as Rayleigh surface waves (named after John W. Strutt, 3rd Baron Rayleigh who first studied them in 1885). The particles in a solid, through which a Rayleigh surface wave passes, move in elliptical paths, with the major axis of the ellipse perpendicular to the surface of the solid. As the depth into the solid increases the "width" of the elliptical path decreases.

Rayleigh waves in an elastic solid are different from surface waves in water in a very important way. In a water wave all particles travel in clockwise circles. However, in a Rayleigh surface wave, particles at the surface trace out a counter-clockwise ellipse, while particles at a depth of more than 1/5th of a wavelength trace out clockwise ellispes. This motion is often referred to as being "retrograde" since at the surface, the horizontal component of the particle motion is in the opposite direction as the wave propagation direction. I have identified two particles in orange in this animation to illustrate the retrograde elliptical path at the surface and the reversal in the direction of motion as a function of depth.

The Rayleigh surface waves are the waves that cause the most damage during an earthquake. They travel with velocities slower than S waves, and arrive later, but with much greater amplitudes. These are also the waves that are most easily felt during an earthquake and involve both up-down and side-to-side motion.

Update (Aug. 5, 2016): Thanks to Dongyao Li (graduate student at the University of Illinois, Urbana-Champaign) who asked questions resulting in a much improved version of this animation.

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Another example of waves with both longitudinal and transverse motion may be found in solids as Rayleigh surface waves (named after John W. Strutt, 3rd Baron Rayleigh who first studied them in 1885). The particles in a solid, through which a Rayleigh surface wave passes, move in elliptical paths, with the major axis of the ellipse perpendicular to the surface of the solid.

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The home page for Dan Russell's acoustic animations

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The home page for Dan Russell's acoustic animations

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The links below contain animations illustrating acoustics and vibration, waves and oscillation concepts. I started using Mathematica to create animations to help me understand and visualize certain acoustics and vibration phenomena in 1992 while I was a Ph.D. student in the Graduate Program in Acoustics at Penn State. For the next 16 years (1995-2011) I was a physics professor at Kettering University and continued creating animations and using them as educational tools for the courses I was teaching about waves and acoustics. Sometime around 1998 or so I began writing webpages and adding them to this online collection. Now that I'm back at Penn State, teaching graduate level acoustics, I'm continuing to add to my collection of animations. My intent has always been to create physically and mathematically correct animations, accompanied by explanatory text, that illustrate complicated phenomena involving waves and vibration in a manner that aids student understanding. I hope you find these animations useful.

Sound Waves and Sources

Basic Wave Phenomena

Longitudinal Sound Waves

Sound Sources, Radiation, and Scattering

More Complicated Wave Phenomena

Room Acoustics

Vibration and Structural Waves

Vibration of 1-DOF Simple Oscillators

Vibration of Multi-DOF Systems

Vibrational Modes of Continuous Systems

Animations of Experimental Results

Miscellaneous Animations

A New Animation Creator

My current Ph.D. student, Noah Parker, is beginning to develop his own interactive animations to help undergraduate students learn about acoustics, engineering, and physics. Noah Parker's website of Interactive Animations

How do Sine and Cosine relate to the Unit Circle? => webpage with interactive animations showing how trig functions like sine, cosine, and tangent functions relate to the unit circle. New Animation => 2023 => (supported NYU Teaching Advancement Grant with Susie Levi)

Interactive Mathematica CDF files for Illustrating Acoustic Phenomena

The interactive plots in these links contain Mathematica Computable Document Format files and require the use of the free Wolfram CDF Player.

Giving Credit Where Credit is Due

I learned how to use Mathematica to create animations of waves and oscillation phenomena from Dr. Victor Sparrow, my PhD advisor at Penn State. Here is collection of several of his earliest animations from 1992-2000.

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The links below contain animations illustrating acoustics and vibration, waves and oscillation concepts. I started using Mathematica to create animations to help me understand and visualize certain acoustics and vibration phenomena in 1992 while I was a Ph.D. student in the Graduate Program in Acoustics at Penn State.

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Whale facts on Smithsonian website

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Acoustic Intensity Acoustic impedence and specific acoustic impedence - dosits

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Acoustic Intensity Acoustic impedence and specific acoustic impedence - dosits

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Animals can detect these different aspects of sound.  Some species, such as marine fishes and some invertebrates are thought to use particle motion; others, such as marine mammals, are thought to detect intensity and therefore use both pressure and velocity components.

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https://airtightnesssolutions.co.uk/acoustic-testing-glossary-symbols/

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READ THIS! UNDERWATER SOUND AND THE MARINE MAMMAL ACOUSTIC ENVIRONMENT A Guide to Fundamental Principles

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READ THIS! UNDERWATER SOUND AND THE MARINE MAMMAL ACOUSTIC ENVIRONMENT A Guide to Fundamental Principles

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The Otolith Group - Otolith literally means 'Ear stones' (Dosits website)

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The Otolith Group - Otolith literally means 'Ear stones' (Dosits website)

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The Otolith Group was founded by the artists, curators and theorists Anjalika Sagar and Kodwo Eshun in London in 2002. They work by seeing and listening across media, from deep time to the cosmos, opening up human and non-human life to an aesthetics of intertemporality and interscalarity.

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Audio on my computer

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Boats and boating--Equipment and supplies

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"The fetal baleen whale grows fast in the womb, 2.7 centimeters per day for an unborn blue.11 After birth, the calves suckle on the rich milk of their mothers, 20–50 percent fat, the fast growth continues, so that the calf has added about 60 percent of its mother’s length by its first birthday.12"p70

"The bowhead lives its life extremely slowly, becoming sexually mature at about age twenty-five, with females giving birth every seven years or so; if it avoids the whalers, a bowhead has a good chance of living well past a century.19 It is definitively the end of the slow life-history spectrum."p71

"The other baleen whales don’t form surface active groups when breeding in any obvious way, but this does not mean an absence of sociality. As we will discuss in the next two sections, sounds seem to be an important part of the mating process for baleen whales, and the whales can hear each other over large ranges. The animals may well be interacting in significant ways but be too far apart for humans to consider them part of the same group—or even to see them together. This mismatch between what is likely meaningful for the whales and what we humans can see is a problem for our understanding of all the cetaceans but perhaps especially for the baleen whales, whose sounds are so loud and carry over such long ranges."p74

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LISTEN AND DOWNLOAD! Free Library of whale sounds

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LISTEN AND DOWNLOAD! Free Library of whale sounds

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The Marine Mammal Center conducts basic research, using cutting-edge technology to solve major scientific and conservation challenges. Its scientists and engineers integrate diverse approaches and methods to understanding marine mammals and the different ways humans may influence their health, populations, and ecosystems.

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A coda in music is a passage which brings a piece of music to an end. A coda in whale sounds is a distinctive call belonging to an individual whale.

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In music, a coda (pronounced ; Italian for 'tail'; plural code) is a passage that brings a piece (or a movement) to an end. It may be as simple as a few measures, or as complex as an entire section.

Coda from Mozart's Piano Sonata no. 7 in C Major, K. 309, I, mm. 152-155 Play .[2]

The presence of a coda as a structural element in a movement is especially clear in works written in particular musical forms. Codas were commonly used in both sonata form and variation movements during the Classical era. In a sonata form movement, the recapitulation section will, in general, follow the exposition in its thematic content, while adhering to the home key. The recapitulation often ends with a passage that sounds like a termination, paralleling the music that ended the exposition; thus, any music coming after this termination will be perceived as extra material, i.e., as a coda. In works in variation form, the coda occurs following the last variation and will be very noticeable as the first music not based on the theme.

One of the ways that Beethoven extended and intensified Classical practice was to expand the coda sections, producing a final section sometimes of equal musical weight to the foregoing exposition, development, and recapitulation sections and completing the musical argument. For one famous example, see the finale of Symphony No. 8 (Beethoven).[page needed ]

Musical purpose

Charles Burkhart suggests that the reason codas are common, even necessary, is that, in the climax of the main body of a piece, a "particularly effortful passage", often an expanded phrase, is often created by "working an idea through to its structural conclusions" and that, after all this momentum is created, a coda is required to "look back" on the main body, allow listeners to "take it all in", and "create a sense of balance."

Codetta ( Italian for "little tail", the diminutive form) has a similar purpose to the coda, but on a smaller scale, concluding a section of a work instead of the work as a whole. A typical codetta concludes the exposition and recapitulation sections of a work in sonata form, following the second ( modulated) theme, or the closing theme (if there is one). Thus, in the exposition, it usually appears in the secondary key, but, in the recapitulation, in the primary key. The codetta ordinarily closes with a perfect cadence in the appropriate key, confirming the tonality. If the exposition is repeated, the codetta is likewise repeated. Sometimes it has its ending slightly changed, depending on whether it leads back to the exposition or into the development sections.

Cauda, a Latin word meaning "tail", "edge" or "trail" is the root of coda and is used in the study of conductus of the 12th and 13th centuries. The cauda was a long melisma on one of the last syllables of the text, repeated in each strophe. Conducti were traditionally divided into two groups, conductus cum cauda and conductus sine cauda ( Latin: "conductus with cauda", "conductus without cauda"), based on the presence of the melisma. Thus, the cauda provided a conclusionary role, similar to the modern coda.

Many songs in rock and other genres of popular music have sections identifiable as codas. A coda in these genres is sometimes referred to as an " outro", while in jazz, modern church music and barbershop arranging it is commonly called a "tag". One of the most famous codas is found in the 1968 single " Hey Jude" by the Beatles. The coda lasted nearly four minutes, making the song's full length at just over the seven-minute mark.

Coda sign

In music notation, the coda symbol, which resembles a set of crosshairs, is used as a navigation marker, similar to the sign. It is used where the exit from a repeated section is within that section rather than at the end. The instruction "To Coda" indicates that, upon reaching that point during the final repetition, the performer is to jump immediately to the separate section headed with the coda symbol. The symbol can be used to provide a special ending for the final verse of a song.

The coda sign is encoded in the Musical Symbols block of Unicode as U+1D10C MUSICAL SYMBOL CODA: 𝄌

1. Benward & Saker (2009). ^ Music in Theory and Practice: Volume II, p.355. Eighth Edition. ISBN 978-0-07-310188-0.

2. For discussion of this coda, and of codas in general, see Rosen, Charles (1988) ^ Sonata Forms, 2nd edition. New York: Norton.

3. Burkhart, Charles. "The Phrase Rhythm of Chopin's A-flat Major Mazurka, Op. 59, No. 2" in Stein, Deborah (2005). ^ Engaging Music: Essays in Music Analysis, p.12. New York: Oxford University Press, ISBN 0-19-517010-5.

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In music, a coda (pronounced ; Italian for 'tail'; plural code) is a passage that brings a piece (or a movement) to an end. It may be as simple as a few measures, or as complex as an entire section.

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Blindfolded dolphins can distinguish between copper, brass and aluminium plates of same dimensions, from a distance.

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Unlock the secrets of marine mammal communication while enjoying your time on the water or observing marine mammals from the shore!
Our platform is perfect for boaters, sailors, kayakers, paddleboarders, and marine mammal enthusiasts. Conduct your own independent research to explore the complex world of dolphin, humpback whale, and manatee vocalizations (more species coming soon!), and contribute to conservation efforts. Turn your on-water adventures into meaningful experiences that help with real-world conservation efforts.

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Unlock the secrets of marine mammal communication while enjoying your time on the water or observing marine mammals from the shore! Our platform is perfect for boaters, sailors, kayakers, paddleboarders, and marine mammal enthusiasts. Conduct your own independent research to explore the complex world of dolphin, humpback whale, and manatee vocalizations (more species coming soon!), and contribute to conservation efforts.

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Sperm Whales 'depredation' of fishing lines

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Sperm Whales 'depredation' of fishing lines

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Gear changes may attract the whales. They remove the fish without touching them. This is super-interesting since it involves a kind of adaptive behaviour and kind of symbiotic living, like urban foxes. They've changed foraging depth in order to do this. Risks are entanglement?

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Fossil specimen of a whale inner ear bone, called a tympanic bulla. This specimen is from the Neogene or Pleistocene of Charleston County, South Carolina and is part of the research collection of the Paleontological Research Institution, Ithaca, New York. Length of specimen is approximately 9.5 cm. Model by Emily Hauf.

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Frequencies of Musical Notes, A4 = 440 Hz

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About the size of a fist - see photo

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The Science

These Fossil Sperm Whale Ear Bones were found in the Southeast USA. The anatomical name for this bone is Tympanic Bulla. These fossils are 10 million years old (Miocene Epoch), which was a period when many recognizably modern animals evolved.

The Story

Whale Ear Bones are more readily fossilized than other bones because they are denser. They were specially developed to protect the delicate auditory tissues of the animal. Whale Ear Bones differ from humans' in that they are specially adapted to hear underwater. Fun fact: Whales don't have external ear holes and vibrate their mandibles to create sounds (snakes do this too!).

DETAILS

SKU: FO-SL0015
Dimensions: Approximately 2.75"L x 1.5"W x 1.5"H
Scientific Name: Scaldicetus sp.
Origin: South East, USA.
Period: Miocene Epoch
Age: 10 Million Years Old
Shipping Restrictions: None.

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These Fossil Sperm Whale Ear Bones were found in the Southeast USA. The anatomical name for this bone is Tympanic Bulla.

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Passed to me by Laura

“...identity codas likely “serve multiple evolutionary functions within the umbrella of social bonding”, similar to human music.”p6

"Given evidence that sperm whale clan dialects are the product of cultural transmission via biased social learning (19), it has been posited that certain coda types act as symbolic markers of clan identity (16, 20–22), but quantitative evidence is lacking. However, recent work
showed that sperm whale clans in both the Atlantic and Pacific Oceans could be computationally distinguished by largely clan-specific “identity codas”, as opposed to “nonidentity codas”made by multiple clans (20). If these identity codas can be used by researchers to tell different clans apart, can they serve a similar function for the whales themselves?"p2

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A brass, spherical Helmholtz resonator based on his original design, circa 1890-1900.

Helmholtz resonance, also known as wind throb, refers to the phenomenon of air resonance in a cavity, an effect named after the German physicist Hermann von Helmholtz. This type of resonance occurs when air is forced in and out of a cavity, causing the air inside to vibrate at a specific natural frequency. The principle is widely observable in everyday life, notably when blowing across the top of a bottle, resulting in a resonant tone.

The concept of Helmholtz resonance is fundamental in various fields, including acoustics, engineering, and physics. The resonator itself, termed a Helmholtz resonator, consists of two key components: a cavity and a neck. The size and shape of these components are crucial in determining the resonant frequency, which is the frequency at which the system naturally oscillates.

In the context of acoustics, Helmholtz resonance is instrumental in the design and analysis of musical instruments, architectural acoustics, and sound engineering. It is also utilized in automotive engineering for noise reduction and in designing exhaust systems.

The underlying principle involves the vibration of the air mass in the neck of the resonator, acting analogously to a mass on a spring. When external forces, such as airflow, disturb this air mass, it oscillates and causes the air within the cavity to resonate. This phenomenon is characterized by its sharp and high-amplitude resonance curve, making it distinct from other types of acoustic resonance.

Since its conceptualization in the 19th century, Helmholtz resonance has continued to be a subject of study and application, illustrating the interplay between simple physical systems and complex vibrational phenomena.

A selection of Helmholtz resonators from 1870, at Hunterian Museum and Art Gallery in Glasgow.

Helmholtz described in his 1862 book On the Sensations of Tone an apparatus able to pick out specific frequencies from a complex sound. The Helmholtz resonator, as it is now called, consists of a rigid container of a known volume, nearly spherical in shape, with a small neck and hole in one end and a larger hole in the other end to emit the sound.

When the resonator's 'nipple' is placed inside one's ear, a specific frequency of the complex sound can be picked out and heard clearly. In his book Helmholtz explains: When we "apply a resonator to the ear, most of the tones produced in the surrounding air will be considerably damped; but if the proper tone of the resonator is sounded, it brays into the ear most powerfully.... The proper tone of the resonator may even be sometimes heard cropping up in the whistling of the wind, the rattling of carriage wheels, the splashing of water."

A set of varied size resonators was sold to be used as discrete acoustic filters for the spectral analysis of complex sounds. There is also an adjustable type, called a universal resonator, which consists of two cylinders, one inside the other, which can slide in or out to change the volume of the cavity over a continuous range. An array of 14 of this type of resonator has been employed in a mechanical Fourier sound analyzer. This resonator can also emit a variable-frequency tone when driven by a stream of air in the " tone variator" invented by William Stern, 1897.

When air is forced into a cavity, the pressure inside increases. When the external force pushing the air into the cavity is removed, the higher-pressure air inside will flow out. Due to the inertia of the moving air the cavity will be left at a pressure slightly lower than the outside, causing air to be drawn back in. This process repeats, with the magnitude of the pressure oscillations increasing and decreasing asymptotically after the sound starts and stops.

The port (the neck of the chamber) is placed in the ear, allowing the experimenter to hear the sound and to determine its loudness. The resonant mass of air in the chamber is set in motion through the second hole, which is larger and doesn't have a neck.

A gastropod seashell can form a Helmholtz resonator with low Q factor, amplifying many frequencies, resulting in the "sounds of the sea".

The term Helmholtz resonator is now more generally applied to include bottles from which sound is generated by blowing air across the mouth of the bottle. In this case the length and diameter of the bottle neck also contribute to the resonance frequency and its Q factor.

By one definition a Helmholtz resonator augments the amplitude of the vibratory motion of the enclosed air in a chamber by taking energy from sound waves passing in the surrounding air. In the other definition the sound waves are generated by a uniform stream of air flowing across the open top of an enclosed volume of air.

It can be shown that the resonant angular frequency is given by:

( rad/s),

where:

(gamma) is the adiabatic index or ratio of specific heats. This value is usually 1.4 for air and diatomic gases.

is the cross-sectional area of the neck;

is the mass in the neck;

is the static pressure in the cavity;

is the static volume of the cavity.

For cylindrical or rectangular necks, we have:

,

where:

is the equivalent length of the neck with end correction, which can be calculated as : , where is the actual length of the neck and is the hydraulic diameter of the neck;[4]

is the volume of air in the neck,

thus:

.

From the definition of mass density ( ): .

The speed of sound in a gas is given by:

,

thus, the resonance frequency is:

.

The length of the neck appears in the denominator because the inertia of the air in the neck is proportional to the length. The volume of the cavity appears in the denominator because the spring constant of the air in the cavity is inversely proportional to its volume. The area of the neck matters for two reasons. Increasing the area of the neck increases the inertia of the air proportionately, but also decreases the velocity at which the air rushes in and out.

Depending on the exact shape of the hole, the relative thickness of the sheet with respect to the size of the hole and the size of the cavity, this formula can have limitations. More sophisticated formulae can still be derived analytically, with similar physical explanations (although some differences matter). Furthermore, if the mean flow over the resonator is high (typically with a Mach number above 0.3), some corrections must be applied.

Helmholtz resonance sometimes occurs when a slightly open single car window makes a very loud sound, also called side window buffeting or wind throb.

Helmholtz resonance finds application in internal combustion engines , subwoofers and acoustics. Intake systems described as 'Helmholtz Systems' have been used in the Chrysler V10 engine built for both the Dodge Viper and the Ram pickup truck, and several of the Buell tube-frame series of motorcycles.

The theory of Helmholtz resonators is used in motorcycle and car exhausts to alter the sound of the exhaust note and for differences in power delivery by adding chambers to the exhaust. Exhaust resonators are also used to reduce potentially loud engine noise where the dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust. In some two-stroke engines, a Helmholtz resonator is used to remove the need for a reed valve. A similar effect is also used in the exhaust system of most two-stroke engines, using a reflected pressure pulse to supercharge the cylinder .

During the early 2010s, some Formula 1 teams used Helmholtz resonators in their cars' exhaust systems to help even out the flow of gasses that were being used to seal the edges of their diffusers as part of their exhaust blow diffuser systems.

Helmholtz resonators are also used to build acoustic liners for reducing the noise of aircraft engines, for example. These acoustic liners are made of two components:

a simple sheet of metal (or other material) perforated with little holes spaced out in a regular or irregular pattern; this is called a resistive sheet;

a series of so-called honeycomb cavities (holes with a honeycomb shape, but in fact only their volume matters).

Such acoustic liners are used in most of today's aircraft engines. The perforated sheet is usually visible from inside or outside the airplane; the honeycomb is just under it. The thickness of the perforated sheet is of importance, as shown above. Sometimes there are two layers of liners; they are then called "2-DOF liners" (DOF meaning degrees of freedom), as opposed to "single DOF liners".

This effect might also be used to reduce skin friction drag on aircraft wings by 20%.

The Roman Theatre according to Vitruvius, from Wikisource:Ten Books on Architecture/Book V

Vitruvius, a 1st-century B.C. Roman architect, described the use of bronze or pottery resonators in classical theater design.

Helmholtz resonators are used in architectural acoustics to reduce undesirable low frequency sounds ( standing waves, etc.) by building a resonator tuned to the problem frequency, thereby eliminating it.[citation needed ]

Music (instruments and amplification)

In all stringed instruments, from the veena or sitar to the modern guitar and violin, the response curve of the instrument consists of a series of Helmholtz resonance modes associated with the size and shape of the resonance cavity (harmonics of the fundamental cavity mode), as well as vibration dampening from absorption by the resonance cavity material (typically wood). An ocarina is essentially a Helmholtz resonator where the combined area of the opened finger holes determines the note played by the instrument. The West African djembe is related to a Helmholtz resonator with a small neck area, giving it a deep bass tone, but its stretched skin, strongly coupled to the cavity makes it a more complex, and musically interesting, resonant system. It has been in use for thousands of years.[citation needed ] Conversely, the human mouth is effectively a Helmholtz resonator when it is used in conjunction with a jaw harp, shepherd's whistle,[citation needed ] nose whistle, nose flute. The nose blows air through an open nosepiece, into an air duct, and across an edge adjacent to the open mouth, creating the resonator. The volume and shape of the mouth cavity augments the pitch of the tone.

Helmholtz resonance is also used in bass-reflex speaker enclosures, with the compliance of the air mass inside the enclosure and the mass of air in the port forming a Helmholtz resonator. By tuning the resonant frequency of the Helmholtz resonator to the lower end of the loudspeaker's usable frequency range, the speaker's low-frequency performance is improved.

Helmholtz resonance is one of the principles behind the way piezoelectric buzzers work: a piezoelectric disc acts as the excitation source, but it relies on the acoustic cavity resonance to produce an audible sound.

# data[].attributes.attachment_link.description
Helmholtz resonance, also known as wind throb, refers to the phenomenon of air resonance in a cavity, an effect named after the German physicist Hermann von Helmholtz. This type of resonance occurs when air is forced in and out of a cavity, causing the air inside to vibrate at a specific natural frequency.

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Fossil specimen of a whale inner ear bone, called a tympanic bulla. This specimen is from the Neogene or Pleistocene of Charleston County, South Carolina and is part of the research collection of the Paleontological Research Institution, Ithaca, New York. Length of specimen is approximately 9.5 cm. Model by Emily Hauf.

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Fossil specimen of a whale inner ear bone, called a tympanic bulla. This specimen is from the Neogene or Pleistocene of Charleston County, South Carolina and is part of the research collection of the Paleontological Research Institution, Ithaca, New York. Length of specimen is approximately 9.5 cm. Model by Emily Hauf.

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Battery-free wireless imaging of underwater environments

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Battery-free wireless imaging of underwater environments

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https://www.nature.com/articles/s41467-022-33223-x

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Cetaceans may be able to do more complex auditory processing than land mammals.

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Cetaceans may be able to do more complex auditory processing than land mammals.

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Toothed whales have more ganglion cells associated with hearing than terrestrial mammals. Baleen whales have fewer nerve cells associated with hearing compared to toothed whales, but more than terrestrial mammals. Cetaceans also have a lot more ganglion cells associated with each hair cell than do humans and a much larger auditory nerve. All of these adaptations mean that cetaceans may be able to do more complex auditory processing.

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White squares show where I've eliminated either very dark or very green shades to leave 52 colours I'd like to collect. If I guess I could colour grade the samples, but that defeats the purpose of the idea of collecting shades from different seas/ areas/ conditions etc.

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In the first seven months of 2008, eighteen Cuvier's beaked whales (Ziphius cavirostris), four Sowerby's beaked whales (Mesoplodon bidens), five unidentified beaked whales and twenty-nine long-finned pilot whales (Globicephala melas) were reported stranded in the UK and Ireland. Decomposition of those animals investigated puts the predicted time of death at mid-January. Concerns that an unusual mortality event had taken place prompted further investigations. Most carcasses were too decomposed for necropsy. A summary of findings is presented here. Although the initial stranding of five Cuvier's beaked whales in Scotland shared some similarities with atypical mass stranding events linked in time and space to mid-frequency naval sonars, there were two important differences with the remaining strandings during this period. First, the geographical range of the event was very wide and second, the strandings occurred over a prolonged period of several months. Both of these factors could be related to the fact that the mortalities occurred offshore and the carcasses drifted ashore. The cause(s) of this high number of strandings of mixed offshore cetacean species during this period remain undetermined.

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This article has been cited by the following publications. This list is generated based on data provided by Crossref.

Dolman, Sarah J. Evans, Peter G.H. Notarbartolo-di-Sciara, Giuseppe and Frisch, Heidrun 2011. Active sonar, beaked whales and European regional policy. Marine Pollution Bulletin, Vol. 63, Issue. 1-4, p. 27.

Brander, Keith M. Ottersen, Geir Bakker, Jan P. Beaugrand, Gregory Herr, Helena Garthe, Stefan Gilles, Anita Kenny, Andrew Siebert, Ursula Skjoldal, Hein Rune and Tulp, Ingrid 2016. North Sea Region Climate Change Assessment. p. 241.

Parsons, E. C. M. 2017. Impacts of Navy Sonar on Whales and Dolphins: Now beyond a Smoking Gun?. Frontiers in Marine Science, Vol. 4, Issue. ,

Hin, Vincent Harwood, John and de Roos, André M. 2019. Bio‐energetic modeling of medium‐sized cetaceans shows high sensitivity to disturbance in seasons of low resource supply. Ecological Applications, Vol. 29, Issue. 5,

Coombs, Ellen J. Deaville, Rob Sabin, Richard C. Allan, Louise O'Connell, Mick Berrow, Simon Smith, Brian Brownlow, Andrew Doeschate, Mariel Ten Penrose, Rod Williams, Ruth Perkins, Matthew W. Jepson, Paul D. and Cooper, Natalie 2019. What can cetacean stranding records tell us? A study of UK and Irish cetacean diversity over the past 100 years. Marine Mammal Science, Vol. 35, Issue. 4, p. 1527.

Evans, Peter G.H. 2020. European Whales, Dolphins, and Porpoises. p. 159.

Evans, Peter G.H. 2020. European Whales, Dolphins, and Porpoises. p. 73.

Grove, Thomas Senglat, Chloé Petitguyot, Marie Kosiba, Danny and Rasmussen, Marianne H. 2020. Mass stranding and unusual sightings of northern bottlenose whales (Hyperoodon ampullatus) in Skjálfandi Bay, Iceland. Marine Mammal Science, Vol. 36, Issue. 3, p. 1033.

Barile, Cynthia Berrow, Simon and O'Brien, Joanne 2021. Oceanographic Drivers of Cuvier's (Ziphius cavirostris) and Sowerby's (Mesoplodon bidens) Beaked Whales Acoustic Occurrence along the Irish Shelf Edge. Journal of Marine Science and Engineering, Vol. 9, Issue. 10, p. 1081.

Onoufriou, Aubrie B. Gaggiotti, Oscar E. Aguilar de Soto, Natacha McCarthy, Morgan L. Morin, Phillip A. Rosso, Massimiliano Dalebout, Merel Davison, Nicholas Baird, Robin W. Baker, C. Scott Berrow, Simon Brownlow, Andrew Burns, Daniel Caurant, Florence Claridge, Diane Constantine, Rochelle Demaret, Fabien Dreyer, Sascha Ðuras, Martina Durban, John W. Frantzis, Alexandros Freitas, Luis Genty, Gabrielle Galov, Ana Hansen, Sabine S. Kitchener, Andrew C. Martin, Vidal Mignucci-Giannoni, Antonio A. Montano, Valeria Moulins, Aurelie Olavarría, Carlos Poole, M. Michael Reyes Suárez, Cristel Rogan, Emer Ryan, Conor Schiavi, Agustina Tepsich, Paola Urban R., Jorge West, Kristi Olsen, Morten Tange and Carroll, Emma L. 2022. Biogeography in the deep: Hierarchical population genomic structure of two beaked whale species. Global Ecology and Conservation, Vol. 40, Issue. , p. e02308.

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A note on the unprecedented strandings of 56 deep-diving whales along the UK and Irish coast | Marine Biodiversity Records | Cambridge Core

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A note on the unprecedented strandings of 56 deep-diving whales along the UK and Irish coast - Volume 3

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The real time streaming of whale noise would need some kind of really invasive intervention, either polluting in terms of equipment at depth or darts in animals. Which kind of defeats the point. So any 'access', I concluded, would need to be through imagination.

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Found via Mare's news - Filipe tagged a new animal.

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Movebank is coordinated by the Max Planck Institute of Animal Behavior, the North Carolina Museum of Natural Sciences, and the University of Konstanz.

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Seasonal and diurnal patterns of whale song

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Seasonal and diurnal patterns of whale song

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Patterns in blue whale songs show whether the whales are feeding or migrating * MBARI

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Recordings from MBARI's deep-sea hydrophone show that blue whales mostly sing at night when they are feeding, but are more likely to sing during the daytime when they are migrating.