This is about Sound of class 8th

2. 1.Topics to be covered :
 Sound
 Production of sound and How sound travels
 Sound produced by humans
 Sound produced by musical instruments
 How humans hear sound
 Amplitude ,time period and frequency of vibration
 Loudness and Pitch
 Amplitude , time period and frequency of a vibration
 Audible and Inaudible sounds
 Noise or Music
 Noise pollution.

3. 2.Sound:
Vibrations that travel through the air
or another medium and can be heard
when they reach a person's or animal's
ear are called Sound.

4. 3.Production of sound and how sound
travels :
 Sound is produced by a vibrating body.
 The to and fro motion of an object is called
vibration.
 When a object stops vibrating ,it does not
produce any sound.

5. 4.How sound is produced in humans:

6. 5.Sound produced by musical
instruments:
 In musical instruments sound is produced with
the help of vibrating parts.
 In different musical instruments different
parts vibrate to produce sound
 Eg. In tabla stretched membrane vibrates to
produce sound ,in flute air column vibrates to
produce sound ,in sitar strings vibrate to
produce sound.

7. 6.How humans hear sound:
 Human and every animal hears sounds
through their ears.
 Sound Waves enter the ear canal and
cause the eardrum to vibrate. Vibrations
pass through three connected bones in the
middle ear. This motion Sets Fluid Moving
in the inner ear.

8. 7.Amplitude ,time period and Frequency
of a vibration:
Vibration is the to and fro motion of a object . It is also called
oscillatory motion of a object.

9. 8.Loudness and Pitch:

10. 9.Audible and Inaudible sounds:

11. 10.Noise or Musical sound:

12. 11.Noise Pollution

13. 12.Some causes due to which noise
pollution is caused: