A study on acoustic imaging based on beamformer to range spectra in the phase interference method

Abstract

Information on the distance to the target is very important to achieve the practical use of hands-free speech interfaces and nursing-care robots. Many distance measurement methods, which use the time-of-flight (TOF) of a reflected wave measured with reference to the transmitted wave, have been proposed. However, these methods cannot measure short distances because the transmitted wave, which has not attenuated sufficiently at the time of a reflected wave reception, suppresses reflected waves for short distances. We previously proposed an acoustic distance measurement method based on interference between the transmitted and reflected waves, which can be used for distance measurement over a short range using single microphone. This method is referred to the phase interference method. It can estimate the distance to target, but cannot estimate the direction of target. In the present paper, therefore, we propose to achieve acoustic imaging with the phase interference method by using microphone-array instead of single microphone. More specifically, we apply the beamformer to the range spectra calculated from observed signals at each microphone of microphone-array to obtain the spatial information. Finally, we confirm the effectiveness of the proposed method through evaluation experiments in real environments.