Rotational Doppler analysis and demultiplexing of acoustic vortices using a microphone array

In order to solve the problems of both insufficient response at low frequencies and crosstalk suffered by the existing acoustic vortex demultiplexing method using a single rotating microphone, a method using a circular array of microphones is proposed to analyze the rotational Doppler effect and then demultiplex the acoustic vortex. The circular microphone array is used to extract the time-domain sound pressure signals received by a rotating observer, and the rotational Doppler shifts of the extracted signals are obtained. The acoustic vortex is then demultiplexed from the single spectrum at a certain speed and the multiple spectra within a certain speed range, respectively. The results show that the demultiplexing method using the single-spectrum suffers from the failures caused by the extreme Doppler effect and the equal Doppler shift, while the demultiplexing method using the multiple spectra has effectively solved the problems of insufficient response at low frequencies and crosstalk.