On-the-spot calibration of microphone array Transfer Functions for robot audition

This paper investigates the calibration of a microphone array based robot audition system, namely calibration of microphone array Transfer Functions (TFs). There are mainly two methods to obtain TFs: geometrical calculation and measurement. The geometrical calculation has difficulty in simulating robot- and room-acoustics such as diffraction and reflection properties of a robot´s body and a room, and the measurement is accurate but time-consuming and requires expertise on acoustics. Thus, we propose fast and simple on-the-spot calibration of TFs including robot- and room-acoustics. The proposed approach first estimates microphone location and clock-difference by Simultaneous Localization And Mapping (SLAM) using hand clap acoustic signals while a human is walking around a robot. Second, TFs with robot- and room-acoustics are estimated by hand clap acoustic signals and interpolated so that the TFs can be roundly arranged at regular intervals in an online manner. In the evaluation, we calibrated TFs only by 20 hand claps (took only 20 seconds), and the TFs showed considerable improvements in sound source localization and separation compared to geometrically calculated TFs and achieved comparable performance towards the measured TFs which are calibrated by approximately 60 minute recordings.