# How do we count beats?

Books say that one beat constitutes two successive maxima of sound intensity with a minima in between. This is confusing me as the definition of beat period says - it is the time interval between two successive beats ( which would mean four successive maxima with two successive minima in between?)

Should not the beat period be the time consumed by one single beat i.e. two maxima and one minima?

What is the absolute way of counting beats?

## 2 Answers

It is the time difference between successive maxima or successive minima. However, you cannot determine a beat period from less than 2 beats. I assume you are talking about music, because the standard scientific terminology defines the frequency of "beats per second" as Hertz.

When two waves of a slightly different frequency encounter each other you will hear beats, which is nothing more than the two waves interfering with each other first constructively and then destructively, over and over as the waves go in and out of phase with each other. So now forget that there are two waves and concentrate on the sound made by the pair together. Then the beat period T will be the time between successive sounds, and the beat frequency will be the reciprocal f = 1/T of the period.