Sound

1. SOUND

7. eardrum
cochlea auditory
receptor cells frequency
spectrum
nerve impulse

8. The pitch is the highness or lowness of a sound . It depends
almost completely on the frequency of the sound wave . Sound
frequency is the number of sound waves that passes through a
point in a certain amount of time, such as one second . The
greater the frequency, the higher the pitch .
The hertz (Hz) is a unit to measure frequency and so pitch is
measured in hertz . Ultrasonics are sound waves of frequency
above 20 00 Hz . Infrasonics are those of frequency below 20
Hz .
As mentioned earlier, the pitch of sound depends on the
frequency of the sound waves . A change in the frequency of a
sound is known as the Doppler effect .

9. - it is named after the Austrian physicist Christian
Doppler , is the change in the frequency of a sound that is
caused by the movement of either the source or the
listener .

10. Example 1 :

11. Example 2 :

12. The loudness of a sound is determined mainly by the amplitude
of the sound wave . The greater the amplitude of the sound
wave that reaches your eardrums, the greater the perceived
loudness of the sound .
There is an especially defined physical quantity that depends
on the amplitude of sound but is more convenient for relating
amplitude to perceived loudness . This is called sound level or
intensity . The decibel ( dB) is the unit used to measure sound
intensity or loudness .
We are normally exposed to a range of sounds from 0 dB to
about 120 dB . The sound level of the quietest sound that can be
heard under ideal conditions 0 dB; this is called the threshold of
hearing . A sound level of 120 dB which can cause pain and

13. The timbre ( or tone color or tone quality ) of a sound is
used to distinguish between two diff. sounds that have the
same pitch and loudness . This tone quality is very important
since it helps us to identify what produced the sound .
The tone quality of a sound depends on the waveform of the
sound wave . If two sounds have diff. waveforms, we usually
perceive different tone qualities . The simplest waveform is
that of pure tone . Pure tones have a soft, pleasant tone
quality . Complex tones with waveforms that are nearly
sinusoidal share the same characteristics .

16. Density
Elasticity
Temperature

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23. Example :
Interference of sound :

24. Example :

28. Stringed instruments
Examples of Stringed Instruments :

29. Wind instruments
Examples of Wind Instruments :

30. Percussion instruments
Examples of Percussion Instruments :