A physiological sound sensing system using accelerometer based on flip-chip piezoelectric technology and asymmetrically gapped cantilever

This paper focuses on the sensing of physiological sound on human body using accelerometers. The physiological sound sensing have demanding requirements on the sensitivity/noise performance of accelerometers since the physiological sounds are usually very weak. In this paper, a piezoelectric accelerometer based on the asymmetrically gapped cantilever structure, which exhibits significantly improved sensitivity, is presented. Furthermore, in order to reduce the package size of the accelerometer, a flip-chip piezoelectric technology is proposed. The accelerometer has a resonant frequency of 1580 Hz which is much higher than the heart sound frequency range, and a quality factor of 9.2. Using a coherent scaling method, the scaled noise level of the accelerometer between 10 Hz and 400 Hz is 1 μV/√Hz. Preliminarily test results show that the signal-to-noise ratio of the heart sound signal measured by the designed accelerometer is about four times higher than that by a high-end stethoscope.