Sound Source Localization with Front-Back Judgement by Two Microphones Asymmetrically Mounted on a Sphere

In this paper, we propose a novel system to localize a sound source in any planar direction using only two microphones. In our system, the two microphones are asymmetrically placed on a sphere, thus, 1) the diffraction by the sphere and the asymmetrical arrangement of the microphones give the localization cue including the frontback judgment, and 2) unlike the dummy head system, no previous measurements are necessary due to the analytical representation of the sphere diffraction. To deal with reverberation or ambient noises, we consider the maximum likelihood estimation of the direction of arrival with a diffuse noise model on a sphere. We present a real system that we built through the investigation of the optimal microphone arrangement for speech. The experimental results show that our system, which consists of two microphones mounted at ±46◦ angles on a 30mm-radius sphere, estimates a sound source direction including a front-back judgment with less than 10% errors in real environment.