Design of Pseudo-Spherical Microphone Array with Extended Frequency Range for Robot Audition

Microphone arrays constitute the front end for sound acquisition in the auditory system of most humanoid robots. Their design and performance therefore play a central role in robot audition. Although some previous studies are concerned with the optimization of microphone placement for robot audition, spatial aliasing, constituting a major challenge in array design, has not been studied extensively for this application. Spatial aliasing is approached in this paper using a spherical harmonics (SH) framework. A method for microphone positioning that extends the aliasing-free frequency range of low SH orders is developed, and validated by simulation for the design of a microphone array on the head of the humanoid NAO. Aliasing level is significantly reduced compared to the efficient nearly-uniform microphone distribution. The proposed method was employed in the implementation of a 12-microphone array for NAO.