Physics Chapter 22 Sound by

Longitudinal wave

ronaldoyee_161 — 2016-08-03 10:32:18 UTC

1 wavelength is the distance between 2 compressions or rarefactions

Reference: Lee N. 2016. MS981 Chapter 22 Longitudinal Wave [online video]. Singapore. Available from: https://www.youtube.com/watch?v=6GMMFpc8zCc [Accessed: 3 August 2016]

Condition for sound

ronaldoyee_161 — 2016-08-03 10:54:31 UTC

To produce sound, a vibration source is needed
To hear sound, you need a medium; in a vacuum, you cannot hear any sound

Recap!

ronaldoyee_161 — 2016-08-03 10:58:55 UTC

Wave Speed = Frequency * Wavelength

Musical instruments

ronaldoyee_161 — 2016-08-03 11:07:04 UTC

Guitar produce sound by plucking a string
Violin produce sound by bowing a string
Piano produce sound by striking a string
Flute produce sound by blowing air into a tube
Drum and triangle produce sound by striking a surface

Speed of sound

ronaldoyee_161 — 2016-08-03 11:16:16 UTC

In air: 330 m/s
In water: 1500 m/s

Sound travels the slowest in gases and fastest in solid because of the arrangement of molecules

Echo

ronaldoyee_161 — 2016-08-03 11:19:10 UTC

Reflection of sound.
Echos can be used to determine distances (If we know the speed of sound)

Reverberation

ronaldoyee_161 — 2016-08-03 11:22:41 UTC

A sound that sounds like it last longer than usual due to many frequent echos
Concrete walls reflect sound well whereas curtains absorb sound well. Therefore, hotel ballrooms have curtains and carpets, so that speeches can be heard (without too much reverberation) Also, the walls of music venues are made from concrete so that the music can be heard clearly (with reverberation)

Process of hearing sound

ronaldoyee_161 — 2016-08-08 10:31:50 UTC

First, sound is produced by a source.
Next, sound travels in the air as longitudinal wave and lastly, the sound reaches your ears.

Types of sound

ronaldoyee_161 — 2016-08-08 10:34:16 UTC

Infrasound: Frequency < 20Hz
Audible Sound: Frequency from 20Hz to 20000Hz
Ultrasound: Frequency > 20000Hz