A new technique to measure directional impulse responses using a 64-channel spherical microphone

Abstract

A spherical microphone is an array consisting of numerous microphones arranged almost uniformly on the surface of a rigid sphere. Recently, spherical microphone arrays have received attention in architectural acoustics for their ability to characterize the sound field over a full sphere, which can yield additional information about the spatial characteristics of the field, including field diffusivity and directionality of individual reflections. Typically, these arrays are used as real-time analyzers to capture sound pressure information. However, in architectural acoustics, an impulse response measurement is required to adequately characterize the space. An effective approach for utilizing spherical microphones, particularly those with a large number of channels, to capture directional impulse responses has yet to be realized. The current project has utilized a 64-channel spherical microphone to carry out the integrated impulse response measurement technique using a sine-sweep signal. MATLAB has been used to evaluate sound fields in a reverberant chamber using a variety of directionality patterns (e.g., omnidirectional, cardioid, and figure-of-eight). Additionally, work is in progress to allow for arbitrary beamforming and other directionality patterns. Results and analysis will be presented.