Methods to Characterize Sensors for Capturing Body Sounds

Ambulatory monitoring of body sounds is still hindered today by a lack of systematic optimization of sensor, sensor packaging and mounting conditions. This paper presents generic, objective and application-independent evaluation methods that can be used for quantitative on-body sensor optimization. The methods are applied on the evaluation of a thin, bendable and ultra low-power piezoelectric sensor to capture body sounds. The results of this study show that both chest expansion and the pitch of speech can be determined reliably with this sensor, even under conditions of walking, whereas heart sounds can be captured only under quiet, motionless conditions. A low-pass filtering effect of the sensor assembly with a very low cut-off frequency made further investigation of lung sounds impossible. The presented methods can be used in future studies to optimize sensor, sensor packaging and mounting conditions.