Application of the matching pursuit method for the time-scale transformation of the phonocardiogram

A time-scale transformation technique is developed for the phonocardiogram (PCG) based on the matching pursuit method. This method decomposes a signal into a series of time-frequency atoms by using an iterative process. Each atom is the product of a Gaussian window function with a sine wave representing its temporal and spectral properties, respectively. The modification of the time-scale of each atom can be performed without any perceptible change in its spectral components. Therefore, a time-scaled (expanded or compressed) PCG can be derived by the summation of the time-scaled atoms. The technique has been tested on a pathological PCG containing three heart sounds and a murmur. The results showed that the technique is suitable for the time scale transformation of both the transient property of the heart sounds and the more complex random property of the murmurs.