Circular microphone array for robot's audition

The paper describes a "32-channel circular microphone array" which can localize individual sounds from many sound sources in 360 degrees. This microphone array is used in robot audition. Because the microphone array has many microphones, it has tolerance for not only environmental noise but also noise caused by the robot. Moreover, it can localize and separate sound sources in all directions. Sound localization by the microphone array is achieved by a delay-and-sum beamforming algorithm. A dedicated IEEE 1394 32-channel analog-to-digital (A/D) board with microphone amplifier was developed for the microphone array in order to keep a fixed cycle such as a sampling rate of 11 kHz. Sound localization is evaluated by a sound pressure distribution map. A sound localization experiment was conducted with the microphone array mounted on a Nomad mobile robot. One discontinuous sound source, such as music, can be localized accurately. The error margin of sound localization is within about 3/spl deg/. In the future, we will place our microphone array on humanoid robots to confirm system performance in human environment.