DAGA 2013 will take place in Meran, Italy. This is the abstract:

Array modes of compact rigid microphone arrays with unconventional shapes

Fabio Kaiser, Franz Zotter, Filippo Fazi

Compact, rigid spherical microphone arrays and their advantages are well-known. Their

signal processing employs a frequency-independent spherical harmonic decomposition of the microphone signals. A valid far field sound field description is obtained by individual

equalization of the resulting signals by filtering. Any subsequent beamforming achieves an

isotropic spatial resolution and is only a frequency-independent combination of signals. This is possible because the spherical harmonics are modes that separate the scattering problem imposed by the rigid sphere. An analytic separation of such modes for other, more complex array shapes (finite cylinder, finite cone, etc.) is not as easy to find. Nevertheless, these array shapes might be beneficial in applications that desire non-isotropic resolution. This work discusses the calculation of modes for rigid array shapes based on their scattering operator. This operator is numerically described by the boundary element method. Subsequent singular value decomposition of the scattered surface sound pressure due to all plane waves yields the modes and their strengths. The approach promises a similarly simple signal processing as employed with spherical arrays, after the quasi-continuous modes are used for array signal decomposition.