Fast calculation of microphone array steering vectors with shear flow

Abstract

This paper proposes a fast method for calculating the acoustic time delay between an observer and a receiver in a shear flow. This method is applied to an outdoor microphone array measurement on a large-scale wind turbine. In such a set-up, a shear flow represents the actual wind field better than a uniform flow. Steering vectors for beamforming can be obtained by calculating the time delay between each point on a scan grid and each microphone. It is argued that omission in the steering vectors of the decay due to spherical spreading is preferable. Beamforming images show the benefits of ignoring the spherical spreading and of using a shear flow model. It is demonstrated that a shear flow model can also be used in combination with rotating source beamforming, again leading to beamforming improvements.