Cardiac cycle detection for heart sound signal based on instantaneous cycle frequency

A short time cycle frequency spectrum based method is proposed to estimate instantaneous cycle frequency (ICF) for a heart sound signal, which in turn indicates the heart beating frequency (HBF). Cardiac cycles in the signal are thus detected based on the ICF. A cross correlation between adjacent cardiac cycles is further used to compensate for any estimation error of the ICF so as to improve the accuracy of cycle detection. The method is valid for a wide range of heart sound signals even in noisy environment because it exploits the nature of repetition behavior of heart sound. Furthermore, heart sound signal is the only signal source to the method. No any other prior knowledge is required. It can be operated automatically.