Estimation of the distance to sound source based on phase interference using cross-spectrum between actual and pseudo observed waves of a single-channel microphone

The sound source localization problem (identifying the distance and the direction from sound source) has been important in various engineering fields and many approaches have been developed, e.g., MUSIC (MUltiple SIgnal Classification). However, they often require a microphone array with multiple microphone elements to obtain such information. Meanwhile, since the distance to a target is also important, many distance measurement methods with sound have been proposed. We proposed an acoustic distance measurement (ADM) method based on interference between transmitted and reflected waves, which could measure distance at a short range. Existing ADM methods based on interference make errors due to the measuring system from the loudspeaker to the microphone. To remove the effect of the measuring system, a cross-spectral analysis was applied to the observed wave and the pseudo-observed wave, convolving the transmitted wave with the impulse response of the measuring system a priori measured. Attaching a microphone to a target causes multiple reflections (interference between the sound source and the target). This paper describes a method based on the phase interference to estimate the distance between a sound source and a target (reflector), using a single-channel cross-spectrum between the observed and the pseudo-observed waves. The validity and effectiveness of the proposed method is confirmed through simulation and experiment. © 2016 The Institute of Electrical Engineers of Japan.