12. SOUND notes for physics

12. SOUND
Key notes:
1. Sound is produce by vibrations.
2. Sound waves are longitudinal waves.
3. Sound waves consists of a series of compressions and rarefactions that move
through the medium.
4. One wavelength of the sound wave is the distance between two consecutive
compressions or rarefactions.
5. The range of audible frequencies for man is from 20 Hz to 20kHz.
6. Sound waves need a material medium for transmission.
7. Sound travels faster in liquids than in gases and fastest in solids.
8. Sound obeys the laws of reflection.
9. Echoes are caused by the reflection of sound.
10. The loudness of a sound increase if the amplitude of the sound wave increases.
11. The pitch of a sound increases if its frequency increases.
12. The same musical note from different musical instruments has different
qualities.
Formulas:
 SOUND WAVES
Speed = frequency x wavelength
v = fλ
 SPEED OF SOUND
The speed of sound = distance traveled / average time taken
= d / t
 Uses of Echoes
d = vt / 2
d - depth of sea
v - speed of sound
t - time between transmission & reception of sound