Localization of Rotating Sound Sources Using Time Domain Beamforming Code

Abstract

The motion of an acoustic source produces a Doppler shift of the source frequency which is dependent on the source’s motion relative to the receiver. Some applications in acoustics involve rotating sound sources around a fixed axis in space. For example, the noise emitted by fans is of interest and because of the fast rotation, the sound sources are not easy to locate with the standard Delay-and-Sum Beamforming code. In the time domain approach for stationary sound sources, the Delay-and-Sum Beamforming works with shifting the microphone signals due to their different delays caused by the different distances between the source and the microphones and summing them up. This approach is adapted to a moving source, resulting in time dependent delays. The delays are calculated via an advanced time approach where the time at the receiver is calculated from the emission time $\tau$ plus a time dependent delay due to the time dependent distance $r(\tau )$. In contrast to the standard beamforming code, this time domain beamforming code allows to treat rotating sound sources as well as stationary sound sources. In this chapter the differences between the standard Delay-and-Sum Beamforming to the rotating time domain beamforming is shown and examples are presented.