Patent ID: 7438689
Filing Date: 2008-10-21
Classification: A61B

Abstract:
1. A method for arbitrary time and/or frequency scaling by analysis, classification and subsequent re-synthesis of phonocardiographic signals obtained from a transducer and subjected to digital spectral analysis, characterised in that the signals are converted on a running basis to a sinusoidal model representation, that a time and/or frequency axis scaling is defined and used to control the amplitudes and phases of the sinusoids, which are subsequently added to create a time and/or frequency scaled representation of the phonocardiographic signal and comprising the further steps of: obtaining the frequency content of the signal by applying a Short Time Fourier Transform with overlapping segments, a Discrete Fourier Transform being performed on each segment, performing a frequency peak search on each segment by consecutive removal of the spectral components having the highest energy content, identifying each peak by its frequency value repeating the peak search until a maximum number of peaks have been identified or until the energy content of the last peak is below a preset minimum, establishing a segment-by-segment map of spectral peaks, said peaks forming a track over time optionally subjecting the frequency values of the spectral peaks to a multiplication defining a synthesis frame [frame m] of time, based on said segments optionally subjecting each frame to a multiplication of the time scale adjusting the phase of sine generators centered on the frequencies of the tracks adjusting the amplitudes of said sine generators summing the outputs of all sine generators active at any one instant for a given frame length T.