Abstract
With a sound sensing system using stochastic resonance (4SR), it became possible to obtain an acoustic pulse wave (APW)—a waveform created via a mixture of apex beat and heart sound. We examined 50 subjects who were healthy, with no underlying cardiovascular diseases. We could determine boundary frequency (BF) using APW and phonocardiogram signals. APW data was divided into two bands, one from 0.5 Hz to BF, and a second one from BF to 50 Hz. This permitted the extraction of cardiac apex beat (CAB) and cardiac acoustic sound (CAS), respectively. BF could be expressed by a quadratic function of heart rate, and made it possible to collect CAB and CAS in real time. According to heart rate variability analysis, the fluctuation was 1/f, which indicated an efficient cardiac movement when heart rate was 70 to 80/min. In the frequency band between 0.5 Hz and BF, CAB readings collected from the precordial region resembled apex cardiogram data. The waveforms were classified into five types. Therefore, the new 4SR sensing system can be used as a physical diagnostic tool to obtain biological pulse wave data non-invasively and repeatedly over a long period, and it shows promise for broader applications, including AI analysis.
Highlights
With a sound sensing system using stochastic resonance (4SR), it became possible to obtain an acoustic pulse wave (APW)—a waveform created via a mixture of apex beat and heart sound
The correlation diagram between boundary frequency (BF) and heart rate was made using a combination of two BF extraction methods, one of which was based on the frequency of disappearance of higher harmonic vibration, and the other using short time Fourier transform (STFT)
The actual measurement results indicated that BF could be expressed by a quadratic function of heart rates, enabling the determination of BF via front acoustic pulse wave (F-APW) data only and in real time, without the use of a PCG
Summary
With a sound sensing system using stochastic resonance (4SR), it became possible to obtain an acoustic pulse wave (APW)—a waveform created via a mixture of apex beat and heart sound. Front CAB Cardiac apex beat waveform drawn from F-APW Front CAS Cardiac acoustic sound waveform drawn from F-APW HR Heart rate HRV Heart rate variability MAV Micro acoustic vibration PCG Phonocardiogram SBP Systolic blood pressure STFT Short time Fourier transform. gyrocardiography[5] has not been able to reproduce the ACG waveform Both methods are mainly used for time phase analysis. In 2015, we completed a sound sensing system using resonance ( 3SR6,7) with a mechanical amplification mechanism using a harmonic oscillator
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