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In this padlet I am explaining the theory of human hearing. I will be explaining the physiology of hearing, the causes of hearing loss, and the localisation of sound as well as giving out advice on how to protect your ears and show my findings from my own experiment.

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Hearing is when sound travels through the air into our ear and into our brain,In short there are 4 parts:
1.Sound Transmission through the Outer Ear
2. Sound Transmission through the Middle Ear
3.Sound Transmission through the Inner Ear
4. Sound Transmission to the Brain

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There are 3 main parts of the ear:
1. Outer Ear- This is the part we see and it has 2 main parts the Pinna (which collects and directs sound waves traveling in air into the ear canal) and the Ear Canal (approximately 1.25 inches long and .25 inch in diameter its main job is to direct airborne sound waves towards the tympanic membrane (eardrum). The ear canal resonates sound waves and increases the loudness of the tones in the 3000-4000 Hz range.)
2. Middle Ear-The tympanic membrane or eardrum serves as a divider between the outer ear and the middle ear structures.The eardrum is very sensitive to sound waves and vibrates back and forth as the sound waves strike it. The three main features of the middle ear are the Middle Ear Cavity (extends from the ear drum and is about 2 cubic cm in volume),The eustachian tube ( this equalises the air pressure when the tube opens normally by chewing or swallowing the pressure between the outer ear and inner ear is equal-this allows the sound to travel through more easily compared to if it was uneven the ear drum would be in discomfort as the sound would travel through as the ear drum would be forced outward and inward), lastly is the Ossicular Chain (The ossicular chain amplifies a signal approximately 25 decibels as it transfers signals from the tympanic membrane to the inner ear).Three main  bones in the middle ear: the hammer (malleus), the anvil (incus) and the stirrup (stapes)-this helps the sound reach the oval window.
3.Inner Ear-  Made up of two components, The Vestibular (The balance part of the ear and  helps to maintain balance regardless of head position or gravity,)The cochlea -The hearing part of the inner ear is composed of three fluid-filled chambers that extend the length of the structure. The basilar membrane is a structural element that divides the cochlea – which is essentially a long tube – down the middle into two liquid-filled tubes: the scala media and the scala tympani. This is where we detect the frequency of the sound. The two outer chambers are filled with a fluid called perilymph which cushions the delicate structure which is the outer chamber. The 3rd fluid filled chamber is called the cochlear duct which contains the Basilar membrane upon which lies the Organ of Corti. This  is the receptor organ for hearing and the main function of the organ of Corti is to transduce auditory signals and minimise the hair cells’ extraction of sound energy.

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Hearing loss can be temporary or permanent. Different causes include:
-sudden hearing loss due to wax, this may be in one ear, or from a loud noise which may only be temporary
-Gradual hearing loss in one ear may be due to something inside the ear, such as fluid  a bony growth or a build-up of skin cells, it can also be caused by ageing or exposure to loud noises over time.
-A sensorineural hearing loss is defined as damage to the hair cells in the cochlea (this is the sensory hearing organ) or damage to the neural pathways of hearing (nerves).
Treatments include a hearing aid or perhaps sign languages and regularly looking after your ears.You can protect your ears by wearing ear protection at loud concerts or at work with machinery.  This is very important especially if you are a musician as you would not want to decrease your hearing frequency range which can happen with exposure to loud music- this would result in not being able to hear certain frequencies which you may need if you wanted to work in a studio and mix etc.......

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Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance. The auditory system uses several cues for sound source, including time- and level-differences (or intensity-difference) between both ears, spectral information, timing analysis, correlation analysis, and pattern matching. Localization can be described in terms of three-dimensional position:
1. The azimuth or horizontal angle-This is to do with the arrival times between ears
2.The elevation or vertical angle, The amplitude of the sound
3.The distance-are the loss of amplitude, the loss of high frequencies, and the ratio of the direct signal to the reverberated signal
In short, localisation helps us figure out if someone is calling us and from where, it tells us where a sound is coming from!

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Having researched the above and having conducted my own experiment I feel I understand the human ear a lot better. Localisation is a great tool and i feel it can be utilized more in my recordings to help give the affect that an instrument is further away or panned to a particular side by recording with a similar technique that we did for our experiment. this is something that i definitely want to try out at home when recording two guitars-especially for the harmonized solos/sections because I can give the effect that there is two different guitar payers in the band. One harmonized section coming through more to the right microphone and the delayed effect to the left and then the other harmonized section recorded with the left side picking up the sound first then the delayed effect happening with the right microphone. Im very interested to hear how this will sound.

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Myself and a fellow class mate conducted an experiment to show how placing the mics further apart from the sound source (in this case me playing guitar) would affect how quickly the mics pick up the sound. We used 2 dpa 4090 microphones and placed them at either side of my class mates head (beside his ears-picture included). Below is an mp3 of our recording. I played guitar in the left side of the room first, then moved to the front of the microphones then to the right side of the room. Our hypothesis was that the microphones would simulate how the human ears pick up sound waves therefore the left microphone would pick up the sound before the right microphone when I played at the left side of the room because that is where the sound originated. We noticed when playing in front of the mics the sound traveled and sounded more equal compared to when it was at the left/right it sounded more dominant in the respective microphones.  After analyzing  the audio that was recorded we could conclude that our hypothesis was infect correct. To show this was the case I have included a screenshot of the audio that was recorded. In this screenshot the top sound wave was the right mic and the bottom the left mic, I was playing in the left side of the room. You can clearly see that the left microphone picked up the sound first and top (right) had a delayed effect this is called inter-aural delay. This is how humans can perceive sound being from different directions.

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http://www.workplaceintegra.com/hearing-articles/Ear-anatomy.html
https://en.wikipedia.org/wiki/Organ_of_Corti
https://www.nhs.uk/conditions/hearing-loss/\
https://www.hearinglink.org/your-hearing/types-causes-of-hearing-loss/what-is-sensorineural-hearing-loss/
https://www.hear-it.org/The-middle-ear-1
https://www.scienceabc.com/humans/basilar-membrane-what-is-it-and-what-does-it-do.html