Phonocardiogram event-based delineation method using continuous wavelet transform

Abstract

Objective: This paper represents a new method of Phonocardiogram delineation using the heart sound events extracted from the Continuous Wavelet transformation of the Phonocardiogram. Methods: The Phonocardiogram signals were filtered using the Chebyshev bandpass Type-II filter to remove the noise. A two-dimensional Time-Frequency Continuous Wavelet Transform operator was applied to the Phonocardiograms to convert the audio signal into the time-frequency Spectrogram. The Row sum of the Spectrogram matrix was evaluated by summing the matrix for all frequencies along with the time axis. The average of the row sum was calculated. This average value was then subtracted from the row sum. The intersection of the deduced row sum, after subtraction, indicated the boundaries of the Phonocardiogram. Beat identification in the Phonocardiogram was done using Fast Fourier Transform. Conclusion: The method can identify the boundaries of the sounds in the Phonocardiogram and indicate the presence of the First heart sound-systole-Second heart sound-diastole sequence with an accuracy of 90.1% and an F1 score of 94.8%. Significance: The method can be used to delineate Phonocardiograms without any external reference like ECG, PPG, or carotid Pulse. No additional signal processing overheads like noise threshold, activity detection, or feature extraction are involved.