TIME-FREQUENCY SCALING TRANSFORMATION OF THE PHONOCARDIOGRAM BASED OFTHE MATCHING PURSUIT METHOD

A time-frequency scaling transformation based on the matching pursuit (MP) method is developed for the phonocardiogram (PCG). The MP method decomposes a signal into a series of time-frequency atoms by using an iterative process, The modification of the time scale of the PCG can b e performed without perceptible change in its spectral characteristics . It is also possible to modify the frequency scale without changing t he temporal properties. The technique has been tested on 11 PCG's cont aining heart sounds and different murmurs. A scaling/inverse-scaling p rocedure was used for quantitative evaluation of the scaling performan ce. Both the spectrogram and a MP-based Wigner distribution were used for visual comparison in the time-frequency domain. The results showed that the technique is suitable and effective for the time-frequency s cale transformation of both the transient property of the heart sounds and the more complex random property of the murmurs. It is also shown that the effectiveness of the method is strongly related to the optim ization of the parameters used for the decomposition of the signals.