Binaural reproduction of spherical microphone array signals

An efficient method for the production of binaural audio signals from spherical microphone array signals using head related impulse responses (HRIRs) is presented. The processing is done directly in the spherical Fourier transform domain which offers significant speed advantages over the conventional method of beamforming toward each HRIR measurement point. The encoding of HRIRs into the spherical Fourier domain is complicated by the fact that the available HRIR databases (CIPIC, MIT, KEMAR) use irregular sampling positions around the sphere and do not contain data for sound coming from angles below the subject. However, for spatially bandlimited processing it is possible to use an LMS technique with regularization to perform the spherical Fourier transform of these HRIRs. A real-time system with head-tracking using the eigenmike (TM) and the CIPIC HRIR database is presented which processes spherical harmonics up to third order. Since the head-rotation operation is performed digitally, this technique is especially useful for remote surveillance and virtual reality systems with complex acoustic scenes.