Spindle-Torus Sampling for an Efficient-Scanning Spherical Microphone Array

Spherical microphone arrays have been studied for a wide range of applications. In particular, microphones arranged around an open sphere in scanning microphone array configurations are useful for sound field analysis. However, it has been shown that open-sphere arrays have poor robustness at the null frequencies of the spherical Bessel functions. Alternative configurations that overcome this problem have been presented, including the dual-sphere configuration, which requires to double the total number of spatial samples, and the shell configuration, which is difficult to implement with a scanning system. This paper presents a new spindle-torus sampling configuration, which achieves high robustness with a relatively small number of sampling points. The special geometry of the torus surface is realized using two rotating tables and a mechanical offset, which facilitates conducting a measurement session with a fully automatic scanning using a single microphone. PACS no. 43.60.Fg