Doppler effect in the time-domain beamforming for rotating sound source identification

Abstract

Identifications of rotating sound sources are of interest in many industrial applications. The most famous beamforming to identify rotating sound source is the time-domain ROSI beamforming proposed by Sijtsma et al. (AIAA 2001-2167, 2001). Nowadays ROSI is still the unique widely recognized beamforming for array with arbitrary microphone configuration to identify rotating sound source. De-Dopplerisation is essential for beamforming to identify a moving sound source. This paper is devoted to the identification and elimination of the Doppler effect in ROSI. A non-zero source with a fundamental frequency may induce ghost contributions in ROSI at other scan points different from this source position, at all side band frequencies to the fundamental frequency with a modulation frequency equal to the rotation frequency. A rotational symmetry array with respect to rotation axis of sound source can be used to eliminate the ghost contributions in ROSI at side bands that are not non-zero integer multiples on the order of rotational symmetry with respect to the rotation axis of sound source of the array.