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.