Maximum length sequence and Bessel diffusers using active technologies

Cox, TJ ORCID:, Avis, MR and Xiao, L 2006, 'Maximum length sequence and Bessel diffusers using active technologies' , Journal of Sound and Vibration, 289 (4-5) , pp. 807-829.

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Active technologies can enable room acoustic diffusers to operate over a wider bandwidth than passive devices, by extending the bass response. Active impedance control can be used to generate surface impedance distributions which cause wavefront dispersion, as opposed to the more normal absorptive or pressure-cancelling target functions. This paper details the development of two new types of active diffusers which are difficult, if not impossible, to make as passive wide-band structures. The first type is a maximum length sequence diffuser where the well depths are designed to be frequency dependent to avoid the critical frequencies present in the passive device, and so achieve performance over a finite-bandwidth. The second is a Bessel diffuser, which exploits concepts developed for transducer arrays to form a hybrid absorber–diffuser. Details of the designs are given, and measurements of scattering and impedance used to show that the active diffusers are operating correctly over a bandwidth of about 100 Hz to 1.1 kHz. Boundary element method simulation is used to show how more application-realistic arrays of these devices would behave.

Item Type: Article
Themes: Subjects / Themes > Q Science > QC Physics > QC221-246 Acoustics - Sound
Subjects outside of the University Themes
Schools: Schools > School of the Built Environment
Schools > School of Computing, Science and Engineering > Salford Innovation Research Centre
Journal or Publication Title: Journal of Sound and Vibration
Publisher: Elsevier
Refereed: Yes
ISSN: 1095-8568
Depositing User: H Kenna
Date Deposited: 10 Sep 2007 13:01
Last Modified: 16 Feb 2022 07:46

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