Audio Capture Using Structural Sensors on Vibrating Panel Surfaces

The microphones and loudspeakers of modern compact electronic devices such as smartphones and tablets typically require case penetrations that leave the device vulnerable to environmental damage. To address this, the authors propose a surface-based audio interface that employs force actuators for reproduction and structural vibration sensors to record the vibrations of the display panel induced by incident acoustic waves. This paper reports experimental results showing that recorded speech signals are of sufficient quality to enable high-reliability automatic speech recognition despite degradation by the panel’s resonant properties. The authors report the results of experiments in which acoustic waves containing speech were directed to several panels, and the subsequent vibrations of the panels’ surfaces were recorded using structural sensors. The recording quality was characterized by measuring the speech transmission index, and the recordings were transcribed to text using an automatic speech recognition system from which the resulting word error rate was determined. Experiments showed that the word error rate (10%–13%) achieved for the audio signals recorded by the method described in this paper was comparable to that for audio captured by a high-quality studio microphone (10%). The authors also demonstrated a crosstalk cancellation method that enables the system to simultaneously record and play audio signals.