1. Physics Chapter 15: Sound Day 1 Notes
Sound waves are longitudinal waves.
source compression rarefaction
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| | wavelength

2. The Speed of Sound
The formula for the speed of sound is

3. The Speed of Sound 2 Sound in air at 1 atm travels at 331 m/s at 0oC.
Sound travels faster in solids, then liquids, and slowest in gases.(normally)
The higher the temperature, the higher the speed of sound. The speed of sound at a certain temperature Celsius is:
VT=[331.0 m/s+(TC *.607)]

4. Detection of Sound
The tympanic membrane (ear-drum) perceives sound waves, then vibrates the 3 bones in the middle ear, and the vibrations pass to the fluid-filled cochlea.
Different length hairs sense different frequencies of sound and send a signal via the auditory nerve.

5. Perceiving Sound
Merin Mersene and Galileo first determined that pitch was determined by the highness or lowness of frequency.
Loudness of sound is the intensity of sound determined by the amplitude of the sound wave.
Sound intensities are measured on a power-of-10 scale called sound level, and measured in decibels. (See scale page 413)
(The bel was named after Alexander Graham Bel.)
A 10 dB increase in sound level doubles the loudness of a sound.
Humans can perceive sounds from 20Hz to 20,000Hz.

6. The Doppler Effect
When a sound-source is moving toward you, you hear a higher pitch; when the source moves away, you hear a lower pitch.
This is called the Doppler effect.

7. Frequency Calculations for Doppler effect
Detected frequency for source moving toward you:
vs =v of source
v = speed of sound
f= real frequency
f ’= perceived frequency
See page 415
Detected frequency for source moving away from you: