With the recent widespread availability of inexpensive DVD players and home theater systems, surround sound has become a mainstream consumer technology. The basic recording techniques for live sound events have not changed to accommodate this new dimension of sound field playback. More advanced analysis of sound fields and forensic capture of spatial sound also require new microphone array systems. This chapter describes a new spherical microphone array that performs an orthonormal decomposition of the sound pressure field. Sufficient order decomposition into these eigenbeams can produce much higher spatial resolution than traditional recording systems, thereby enabling more accurate sound field capture. A general mathematical framework based on these eigenbeams forms the basis of a scalable representation that enables one to easily compute and analyze the spatial distribution of live or recorded sound fields. A 24 element spherical microphone array composed of pressure microphones mounted on the surface of a rigid spherical baffle was constructed. Experimental results from a real-time implementation show that a theory based on spherical harmonic eigenbeams matches measured results.
Meyer, J., & Elko, G. W. (2006). Spherical Microphone Arrays for 3D Sound Recording. In Audio Signal Processing for Next-Generation Multimedia Communication Systems (pp. 67–89). Kluwer Academic Publishers. https://doi.org/10.1007/1-4020-7769-6_3