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 dualsphere 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.