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Beamforming for measurements under disturbed propagation conditions using numerically calculated Green’s functions

Lehmann, Marius and Ernst, Daniel and Schneider, Marc and Spehr, Carsten and Lummer, Markus (2022) Beamforming for measurements under disturbed propagation conditions using numerically calculated Green’s functions. Journal of Sound and Vibration, 520, pp. 1-16. Elsevier. doi: 10.1016/j.jsv.2021.116638. ISSN 0022-460X.

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Official URL: https://doi.org/10.1016/j.jsv.2021.116638


Beamforming methods for sound source localization are usually based on free-field Green’s functions to model the sound propagation between source and microphones. This assumption is known to be incorrect for many industrial applications and the beamforming results can suffer from this inconsistency regarding both, main lobe width and dynamic range. The aim of this paper is to investigate whether the use of numerically calculated Green’s functions, which include the diffraction and reflection of the sound path between source and microphones, can improve the results of beamforming measurements. The current test cases of numerical and experimental investigations consist of a source placed in a short rectangular duct. The measurements are performed outside the duct in a semi-anechoic chamber. A typical example for this kind of installation is a fan with a heat exchanger. The Green’s functions for this test case are calculated numerically using the boundary element method. These tailored Green’s functions are used to calculate the corresponding beamforming steering vectors. Beamforming measurements are performed in this paper using a loudspeaker mounted in a disc as a reference source in the heat exchanger duct. The measurements are performed both with stationary and rotating disc. The stationary measurements are evaluated in the frequency domain. For the evaluation of the rotating measurements, a new beamforming method in the time domain is presented. This method also uses the stationary Green’s functions, which were calculated numerically in the frequency domain. It is also shown how the weighting of these tailored Green’s functions can be done for time domain beamforming. By means of different validation criteria it can be shown that the results with the numerical calculated Green’s functions are improved compared to free field beamforming. This is true both in the stationary and rotating case.

Item URL in elib:https://elib.dlr.de/139933/
Document Type:Article
Additional Information:https://www.journals.elsevier.com/journal-of-sound-and-vibration, Article 116638, Available online 30 November 2021
Title:Beamforming for measurements under disturbed propagation conditions using numerically calculated Green’s functions
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Lehmann, Mariusebm-papst Mulfingen GmbH & Co. KG, MulfingenUNSPECIFIEDUNSPECIFIED
Ernst, DanielUNSPECIFIEDhttps://orcid.org/0000-0001-7920-9162UNSPECIFIED
Schneider, Marcebm-papst Mulfingen GmbH & Co. KG, MulfingenUNSPECIFIEDUNSPECIFIED
Spehr, CarstenUNSPECIFIEDhttps://orcid.org/0000-0002-2744-3675UNSPECIFIED
Date:3 March 2022
Journal or Publication Title:Journal of Sound and Vibration
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 1-16
EditorsEmailEditor's ORCID iDORCID Put Code
Series Name:Science Direct
Keywords:Beamforming Disturbed sound propagation Boundary element method Steering vector formulation Tailored Green’s functions
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Efficient Vehicle
DLR - Research area:Aeronautics
DLR - Program:L EV - Efficient Vehicle
DLR - Research theme (Project):L - Virtual Aircraft and  Validation
Location: Braunschweig , Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Experimental Methods, GO
Institute for Aerodynamics and Flow Technology > Technical Acoustics
Deposited By: Micknaus, Ilka
Deposited On:04 Jan 2022 13:00
Last Modified:28 Jun 2023 13:15

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