Performance comparison of different contact microphones used for voice monitoring

The aim of this paper consists in comparing the performances of different sensors used as contact microphones for voice monitoring. Four devices are analyzed: two electret condenser microphones which differ in size, an accelerometer and a piezoelectric transducer. The investigation is based on the analysis of the signal acquired at the output of each sensor when it is attached at the jugular notch, to sense the skin vibration induced by the vocal folds activity. This signal is often used to extract vocal parameters, such as sound pressure level, fundamental frequency, time dose, jitter and shimmer, which are of interest for diagnostic purposes as well as for vocal load assessment. Experimental tests were performed in a sound absorbing chamber using different speech materials. During these tests, a calibrated microphone placed at the fixed distance of 17 cm from the speaker’s mouth was used to ensure measurement traceability. The signals simultaneously acquired at the output of each contact sensor and of the microphone in front of the speaker’s mouth were compared to identify which device better provides exhaustive information of the speech signal. Since the use of these transducers is not intrusive and does not interfere with normal daily activities (e.g. for voice long-term monitoring in working environments), their sensitivity to body movements and to background noise has also been estimated. The frequency response of each sensor compared to one of the signal acquired by the microphone in air was furtherly analyzed.