CHAPTER 3 SOUND
Sound plays a vital role in our daily life. We communicate using sounds.
SOUND AND VIBRATION
Sound is produced by a vibrating body. The to and fro motion of a body is called vibration.
SOUND PRODUCED BY HUMANS
In humans, the voice box or the larynx produces sounds. There are two vocal cords which stretch across the voice box. There is a narrow slit in between the vocal cords for the passage of air.
SOUND AND MEDIUM FOR PROPAGATION
Sound requires a medium for propagation. Sound travels through solid, liquid and air.
At the end of the ear canal, there is a thin membrane that is stretched tightly. This is called eardrum. Sound vibrations reach the eardrum and make it vibrate. This signal goes to the brain and we perceive sound.
The number of oscillations per second is known as the frequency. The unit of frequency is hertz.
LOUDNESS AND PITCH
Loudness is directly proportional to the amplitude. Pitch is directly proportional to the frequency.
NOISE AND MUSIC
Unpleasant sounds are called noise. Music is the sound that is pleasing to the ear.
Noise pollution is the presence of unwanted or loud sounds in the environment.
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