Time-frequency characteristics of the vibrations underlying the first fetal heart sound: a preliminary study.

This work studied, for the first time, the time-frequency characteristics of the vibrations underlying the first fetal heart sound (S1). To this end, the continuous wavelet transform was used to produce time-energy and time-frequency representations of S1 from where five vibrations were studied by their timing, energy, and frequency characteristics in three gestational age groups (early, G1, preterm, G2, and term, G3). Results on a dataset of 1111 S1s (9 phonocardiograms between 33 and 40 weeks) indicate that such representations uncovered a set of five well-defined, non-overlapped, and large-energy vibrations whose features presented interesting behaviors.

Timing the opening and closure of the aortic valve using a phonocardiogram envelope: a performance test for systolic time intervals measurement.

Objective: This work explored the reliability of using points on the heart sounds envelope as indicators of the opening and closure of the aortic valve (AVO, AVC) to measure the pre-ejection period (PEP) and the left ventricular ejection time (LVET).

Approach: 36 phonocardiograms (PCGs) from healthy subjects and cardiovascular disease subjects were denoised using single-channel independent component analysis (SCICA) and, from the Hilbert envelopes, the positions of the S1 and S2 peaks were detected (pS1, pS2). Complementarily, the positions of the local maxima of S1 and S2 (mS1, mS2) and the points surrounding pS1 and pS2 (tS1, tS2) were obtained.

Time-structure based reconstruction of physiological independent sources extracted from noisy abdominal phonograms.

The abdominal phonogram is a signal recorded by a sensitive acoustic sensor positioned on the maternal womb. The signal conveys information that is valuable for fetal surveillance (e.g.