V.V.Krizhanovskii, V.V.Krizhanovskii (jr.)
Some opportunities for improving of spectral-time analysis of the low-frequency acoustic tones of cardiosignals

Acoustic bulletin, Vol. 16 1, (2013-2014) p.33-46
The paper deals with considering of a problem of increasing of efficiency of spectral-time analysis of the low-frequency tones of cardiosignals. The main factors influencing the estimates of power spectral density (PSD) of the tones in the low-frequency area are determined basing on the actual records of acoustic cardiosignals. The structure of estimates of PSD of tones in the low-frequency area is shown to be considerably depending on level of influence of the vibration (seismic) interferences. The algorithm of their adaptive filtration is offered and on its basis the estimates of PSD of tones of the acoustic cardiosignals are obtained. It is noted that the lower bounds of the spectra of the first two tones are located at infrasonic frequencies. It is shown that for the phase of diastole, the offered algorithm allows the revealing of weak low-frequency perturbations in the structure of PSD estimates caused by the presence of the third and fourth tones. On the base of the offered acoustic model for the channel where cardiac signals are propagating, the frequency characteristic of channel transfer function is estimated quantitatively. The observed frequency unevenness of the estimates of PSD of the tones is shown to be determined by the resonances of transfer function.
cardiosignal, cardiac tones, power spectral density, transfer function