Beat

In physics and sound, a beat is the oscillation between zero intensity and full intensity that occurs when two frequencies (which are not harmonically related) are added together, caused by alternating constructive and destructive interference of the pressure waves. Beating is heard as a pulsation in loudness of two nearby frequencies, f₁ and f₂, at the rate of |f₁ − f₂|. Thus f = 0 when the two waves are in unison and as the difference between f₁ and f₂ increases, the speed increases until beyond a certain proximity beating becomes undetectable and a roughness is heard instead, after which the two pitches are perceived as separate. Beating can also be heard between notes that are near to, but not exactly, a harmonic interval. The composer Alvin Lucier has written many pieces which feature interference beats as their main focus. Musicians commonly use interference beats to objectively check tuning at the unison, perfect fifth, or other simple harmonic intervals. (See also heterodyne.)

In music, beat is any of the periodic transient signals in music that mark the rhythm.
- Beat can also mean solely the bass and snare drums of the rhythm. DJs often beatmatch the songs that they play.
- Interference beats are used in tuning, see tuning and physics above.
- musical genre: Beat is a style played in the 1960s.
- The Beat, known in the US as The English Beat, was a UK ska band of the early 1980s.

In literature beat is a genre of literature written by beatniks. See beat generation.

In poetry, beat is sometimes used to refer to metrical feet. There is also beat poetry; see beat generation.

police: Beat is the territory and time that a police officer patrols.

Beating is striking more than once, in violence, beating a drum, etc.

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