Beat counter and method thereof

A rapid and stable beat counter and a method thereof can calculate the beat of an inputted digital sound signal. The method mainly comprises: (i) receiving a digital sound signal; reducing the sampling rate of the digital sound signal while summing the sampling points within each particular range; (ii) smoothing the summed signals and calculating the difference between two sampling points separated for a sampling point; and setting the data points having a difference below zero to zero, thereby obtain a start point peak row; and (iii) comparing the start point peak row with a unit pulse series set of a different period; selecting the period of the unit pulse series, that matches best with the start point peak row, as the possible period of the start point peak row, thereby calculating the beat per minute. Furthermore, in order to increase the stability of the beat counting, the method further comprises a step of increasing the stability for determining whether there is a need to update the beat per minute.