Results on the time-frequency characterization of the first heart sound in normal man

The first heart sound (S1) recorded at four standard auscultatory locations in 80 subjects is analyzed for its time-frequency characteristics. Based on the continuous wavelet transform using the Morlet wavelet function, a methodology to identify the frequency components of the first heart sound together with their time locations with respect to the beginning of each cardiac cycle is proposed. As a result, the summary time-frequency characterization of S1 obtained by this approach is reported.