A novel heart sound activity detection framework for automated heart sound analysis

• Heart sound activity detector (HSAD) is presented based on instantaneous phase waveform of the envelope of a filtered PCG signal.
• Total variation filter provides better noise-reduction while preserving components of heart sounds and murmurs.
• Envelope extractor achieves better nonlinear peak amplification and reduces effect of magnitude of residual noise components.
• Boundaries of heart sounds (S1, S2, S3, S4) and murmurs are automatically determined using instantaneous phase waveform of the envelope.
• HSAD accurately determines the boundaries of low-amplitude heart sounds and murmurs even under low SNR conditions.

In automated heart sound analysis and diagnosis, a set of clinically valued parameters including sound intensity, frequency content, timing, duration, shape, systolic and diastolic intervals, the ratio of the first heart sound amplitude to second heart sound amplitude (S1/S2), and the ratio of diastolic to systolic duration (D/S) is measured from the PCG signal. The quality of the clinical feature parameters highly rely on accurate determination of boundaries of the acoustic events (heart sounds S1, S2, S3, S4 and murmurs) and the systolic/diastolic pause period in the PCG signal. Therefore, in this paper, we propose a new automated robust heart sound activity detection (HSAD) method based on the total variation filtering, Shannon entropy envelope computation, instantaneous phase based boundary determination, and boundary location adjustment. The proposed HSAD method is validated using different clean and noisy pathological and non-pathological PCG signals. Experiments on a large PCG database show that the HSAD method achieves an average sensitivity (Se) of 99.43% and positive predictivity (+P) of 93.56%. The HSAD method accurately determines boundaries of major acoustic events of the PCG signal with signal-to-noise ratio of 5 dB. Unlike other existing methods, the proposed HSAD method does not use any search-back algorithms. The proposed HSAD method is a quite straightforward and thus it is suitable for real-time wireless cardiac health monitoring and electronic stethoscope devices.