Sounds & Vibrations


  • Birds have a ring of cartilage, called syrinx, in their wind pipe.


  • The pitch of sound is determined by its shrillness or flatness.


  • Sounds, of frequency more than 20 kHz, are known as ultrasonic sounds or ultrasound.


  • The S.I. unit of ‘frequency’ is hertz.


  • The S.I. unit of ‘loudness’ of a sound is bel (B).


  • Ultrasounds are produced by dolphins, bats and porpoises.


  • Velocity of sound is 332 meters/second.

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