### 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.

Original language | English |
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Title of host publication | Proceedings of the 7th Berlin Beamforming Conference |

Number of pages | 15 |

Publication status | Published - 2018 |

Event | 7th Berlin Beamforming Conference - Berlin, Germany Duration: 5 Mar 2018 → 6 Mar 2018 Conference number: 7 http://www.bebec.eu |

### Conference

Conference | 7th Berlin Beamforming Conference |
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Abbreviated title | BeBeC 2018 |

Country | Germany |

City | Berlin |

Period | 5/03/18 → 6/03/18 |

Other | The objective of the conference is to contribute to the development of beamforming methods with respect to the localization and quantification of sound sources. In addition, the conference provides a platform for the presentation and discussion of practical results from a wide range of specific implementations. Beamforming with microphone arrays and related techniques have become standard methods in technical acoustics, proven by an ever increasing number of publications at various acoustic conferences. The methods are used in the highly complex field of aero-acoustics, for the sound source localization on moving vehicles, in technical plants and machinery including the automotive industry. A number of companies are offering commercial beamforming systems. At the same time, a large variety of implementations exist in the academic sector as well as tailor-made solutions for special applications. In order to improve the quantitative analysis of the source distributions, inverse methods are becoming increasingly popular. BeBeC provides a forum for a vivid exchange of experiences and opinions. Both theoretical and practical work receive a platform. Competing institutions and companies are encouraged to participate. Comparisons with other acoustic methods are welcome. |

Internet address |

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## Cite this

Sijtsma, P. (2018). Fast calculation of microphone array steering vectors with shear flow. In

*Proceedings of the 7th Berlin Beamforming Conference*[BeBeC-2018-S3]