Construction, calibration, evaluation of spherical microphone array and its application for beamforming

Spatial acoustic, analysis of spatial properties of sound field using spherical harmonic decomposition is one of fundamental problems in modern acoustic and audio/noise signal processing. Consequently design and construction of reliable spherical microphone array as a tool for spatial analysis is crucial. In this paper development and evaluation of such device is presented. Based on simulation 32 channel spherical microphone array in open sphere configuration has been built. Geometry of regular polyhedron is used for distribution of microphone elements over the sphere. In order to maintain signal to noise level custom-made 32channel audio preamplifier has been developed based on SSM 2019.circuit After complete production spherical microphone array has been tested to evaluate its precision and margins of error. To achieve this, standard deviation and standard uncertainty has been calculated for repeated measurements with a standardized pistophone. Results for one of the microphones are used for calibration, and that one is used as reference one. Evaluation has been also done through analysis of latency of system and reputability of impulse response. For this type of spherical microphone array configuration, several beamforming techniques has been developed. Assessment of techniques has been done through analysis of directivity, directivity index and white noise gain.