Beats

When two sound waves of different frequency approach your ear, the alternating constructive and destructive interference causes the sound to be alternatively soft and loud - a phenomenon which is called "beating" or producing beats. The beat frequency is equal to the absolute value of the difference in frequency of the two waves.

Arising from simple interference, the applications of beats are extremely far ranging. Show

Applications of Beats

Subjective tones Missing fundamental effect Police RADAR Doppler pulse detection Radio applications Mulitphonics

Origin of beats Two tone generators

Envelope of Beat Production

Beats are caused by the interference of two waves at the same point in space. This plot of the variation of resultant amplitude with time shows the periodic increase and decrease for two sine waves.

The image below is the beat pattern produced by a London police whistle, which uses two short pipes to produce a unique and piercing three-note sound.