Page 128 - Science Class 08
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All About Sound
• What is Sound? • Terms Related to Sound
• How to Dis nguish Sound? • Sound and Audibility
• Propaga on of Sound • Sound and Various Mediums
• Speed of Sound
WHAT IS SOUND? v We speak using the voice from our throats.
Sound is a form of energy that produces v Wails and giggles come from the throat too.
sensa on of hearing. We can also say that it is Where does air come from in the throat? It
a form of energy and it comes from vibra ons. can’t be anything but breath. It means that
These vibra ons create sound waves which breath creates sound inside the throat and this
move through a medium such as air and water sound goes into the air in the form of a
before reaching our ears. All sounds are a sensa on.
combina on of pure frequencies. A stretched
Let us take some more examples:
rubber band when plucked, it vibrates and
produces sound. We have also heard a variety v When a drum is beaten, a sound is produced.
of sounds from sitar, violin, veena, ringing of v When a flute is played, a sound is produced.
temple bells, chirping of birds, vehicles honking v When we pluck the string of a sitar, a sound
in traffic, dogs barking, pressure cooker is produced.
whistling, crackers burs ng, ra ling and
How does each of these ac vi es affect the air?
breaking of objects. Also, we hear our favourite
song playing in the iPod. While some of these v When a drum is beaten, it vibrates and
causes the air to vibrate with the sensa on
sounds may be pleasant and soothing, some
of its sound.
could be annoying. But, all these are known as
sounds. v When a flute is played, breath (air) is used
and it creates vibra ons in the air.
Let us think over various kinds of sounds to
know how each of them is produced: v When the string of a sitar is plucked, it
v Birds chirp producing sound in the throats. vibrates and causes the air to vibrate.
128 Science-8
