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A periodic increase and decrease in loudness heard when two notes of slightly different frequency are sounded at the same time. If a note of frequency n is heard at the same time as a note of frequency m, the resulting note will have a frequency of about (n + m)/2. However the amplitude of this note will vary from the difference to the sum of the amplitudes of the m and n notes and the frequency (called the beat frequency) of this variation will be (mn). The beating sound produced occurs as the waves successively reinforce and oppose each other as they move in and out of phase. Beating also occurs with radio-frequency waves and is made use of in heterodyne devices. See also interference.

Subjects: Physics — Mathematics.

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