Design of a compact omnidirectional sound camera using the three-dimensional acoustic intensimetry

Abstract

By using the 3D intensimetry algorithm, a sensor probe has a significant advantage at low frequencies, allowing for a compact array cluster that is far smaller than a wavelength. A super-compact 3D sound camera is designed to estimate the direction of arrival by calculating the three-dimensional intensity vectors based on the measured pressure data. An array of flush-mounted MEMS microphones is configured over the spherical surface of a commercial omnidirectional camera with a diameter of 38 mm. Implementing the operation over a wide frequency range requires the scattering caused by the microphone holder and the irregularity of the array’s directional response to be minimized. Although the spherical scattering reduces the effective upper-bound frequency by two thirds, a truncated stellated-octahedral array using five microphones can significantly reduce the spatial bias error at high frequencies. The test results in an anechoic chamber show an average localization error of 3.2° for human voices. The results in a reverberant room with T30 = 0.66 s reveal an average bearing angle error of 6.5° when a source is positioned within two times the critical distance in the interior space. In such a live room, it is demonstrated that the speakers wearing the face masks can be localized in real-time.