2015 Volume 36 Issue 6 Pages 516-526
Sensing of high-definition three-dimensional (3D) sound-space information is of crucial importance for realizing total 3D spatial sound technology. We have proposed a sensing method for 3D sound-space information using symmetrically and densely arranged microphones. This method is called SENZI (Symmetrical object with ENchased Zillion microphones). In the SENZI method, signals recorded by the microphones are simply weighted and summed to synthesize a listener's head-related transfer functions (HRTFs), reflecting the direction in which the listener is facing even after recording. The SENZI method is being developed as a real-time system using a spherical microphone array and field-programmable gate arrays (FPGAs). In the SENZI system, 252 electric condenser microphones (ECMs) were almost uniformly distributed on a rigid sphere. The deviations of the microphone frequency responses were compensated for using the transfer function of the rigid sphere. To avoid the degradation of the accuracy of the synthesized sound space by microphone internal noise, particularly in the low-frequency region, we analyzed the effect of the signal-to-noise ratio (SNR) of microphones on the accuracy of synthesized sound-space information by controlling condition numbers of matrix constructed from transfer functions. On the basis of the results of these analyses, a compact SENZI system was implemented. Results of experiments indicated that 3D sound-space information was well expressed using the system.