TIME-FREQUENCY ANALYSIS OF THE FIRST HEART-SOUND - PART 2 - AN APPROPRIATE TIME-FREQUENCY REPRESENTATION TECHNIQUE

A simulated first heart sound (Sf) signal is used to determine the bes t technique for analysing physiological Sf from the following five tim e-frequency representations (TFR): the spectrogram, time-varying autor egressive modelling, binomial reduced interference distribution, Besse l distribution and cone-kernel distribution (CKD). To provide informat ion on the time and frequency resolutions of each TFR technique, the i nstantaneous frequency and the -3 dB bandwidth as functions of time we re computed for each simulated component of the S1. The performance in dex for selecting the best technique was based on the relative error a nd the correlation coefficient of the instantaneous frequency function between the theoretical distribution and the computed TFR. This index served to select the best technique. The sensitivity of each techniqu e to noise and to small variations of the signal parameters was also e valuated. The results of the comparative study, show that, although im portant limitations were found for all five TFRs tested, the CKD appea rs to be the best technique for the time-frequency analysis of multico mponent signals such as the simulated S1.