Comparison of cavity geometries for a microphone array in an open-jet wind-tunnel experiment

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Abstract

This paper analyses the influence of microphone cavity geometry on beamforming measurements with a turbulent boundary layer present on the microphone array. A 16- microphone array was tested in the anechoic open-jet wind tunnel of the Delft University of Technology. The array was placed on a flat plate mounted flush with the exit nozzle of the wind tunnel. Microphones were installed in three different cavity geometries along with a flush mounted microphone array which was used as a baseline for comparison. The geometries include a chamfered-cylindrical hard-plastic cavity, a chamfered-cylindrical cavity made of melamine foam, and a chamfered-cylindrical cavity with star-shaped protrusions, also made of melamine. The recessed cavities were covered with a 0.026 mm gauge steelwire cloth. A speaker emitting white noise outside of the flow was employed as a sound source. Different flow velocities at the same sound power level for the speaker (and hence different signal-to-noise ratios) were studied. The results obtained with the three cavity geometries are compared with the flush-mounted case in terms of the quality of the acoustic source maps (location and strength of the sound source). The signal-to-noise ratio of the beamforming measurements increased by as much as 30 dB by placing microphones within a conical cavity with melamine foam walls when compared to the flush mounted case.
Original languageEnglish
Number of pages18
Publication statusPublished - 2020
Event8th Berlin Beamforming Conferece - Berlin, Germany
Duration: 2 Mar 20203 Mar 2020
Conference number: 8
http://www.bebec.eu

Conference

Conference8th Berlin Beamforming Conferece
Abbreviated titleBeBeC 2020
CountryGermany
CityBerlin
Period2/03/203/03/20
Internet address

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