The document discusses key aspects of sound including pitch, frequency, loudness, timbre, and types of musical instruments. It explains that pitch is determined by frequency, with higher frequencies producing higher pitches, and is measured in hertz. Loudness depends mainly on the amplitude of sound waves, and is measured in decibels. Timbre allows distinguishing between sounds of the same pitch and loudness based on differences in their waveforms. Musical instruments are also categorized into stringed, wind, and percussion types.

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 :