等価回路モデルを用いた体導音センサの周波数特性推定

抄録

Body-conducted sound sensors have an electret condenser microphone with an exposed diaphragm. By covering the sensor with a urethane elastomer, the sensor can be used as a bioacoustic sensor with high sensitivity and resistance to external noise. The body-conducted sound sensors constructed in the past had different parameters such as contact area, thickness of the propagation layer and mass, and the extent of their influence on frequency characteristics is unclear. This study aimed to investigate the influence of the mass and shape of body-conducted sound sensor on pressure sensitivity. The methods comprised ( 1 ) simulation using the equivalent circuit model, ( 2 ) production of body-conducted sound sensors and measurement systems, and ( 3 ) sensitivity measurements and analyses. The simulation results demonstrated that the sensitivity increased when the body-conducted sound sensor had a small mass and a large contact area. In the sensitivity measurement system, a compact acceleration sensor was used as a reference sensor, and the sensitivity to pressure was calculated. The results obtained from the sensitivity measurement system correlated strongly with the frequency characteristics of the simulations, with a correlation coefficient of 0.90-0.95 in the frequency range of 100-2,000Hz. In the statistical analysis, by varying the mass and contact area, significant differences were observed in the frequency range of 700-2,000Hz while no significant differences were observed in the frequency range of 100-600Hz. Moreover, as a result of reducing the housing mass, sensitivity was increased. In conclusion, body-conducted sound sensors with a small mass and large contact area exhibit high pressure sensitivity in the frequency range of 700-2,000Hz, and their frequency characteristics can be estimated by simulation.