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Boundary element modelling of fractal and other enhanced bandwidth Schroeder diffusers


Lock, A and Holloway, D, Boundary element modelling of fractal and other enhanced bandwidth Schroeder diffusers, Proceedings of the Annual Conference of the Australian Acoustical Society, 15-18 November 2015, Hunter Valley, pp. 1-10. ISBN 978-0-909882-05-1 (2015) [Refereed Conference Paper]


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It is well established that Schroeder diffusers may be used as surface treatment to promote diffuse sound fields in auditoria over a target frequency range. Quadratic Residue Diffusers are very effective within a design frequency bandwidth, and this frequency bandwidth may be significantly extended by a nested or fractal design. Publicly available data typically publishes diffusion coefficients separately for the parent diffuser and the child diffuser, with some ambiguity surrounding the effect the two levels have on each other, and the performance at 'crossover' frequencies. This paper uses an optimised 2D boundary element method to investigate the differences in results when the parent and child diffusers are modelled separately, and as an integrated design. It is found that the scattering properties of the child diffuser are significantly modified by the well of the parent diffuser in which it is placed. More interestingly, the excellent scattering properties of the fractal design may be achieved with only a minor loss of bandwidth using a far simpler and more robust geometry in which the child diffuser is replaced by a concave surface at the base of the well in the parent diffuser. The paper outlines the optimisation of the boundary element code for this task, and compares results for a variety of well bottom shapes with the fractal design.

Item Details

Item Type:Refereed Conference Paper
Keywords:acoustics, boundary element method, Schroeder diffusers
Research Division:Built Environment and Design
Research Group:Architecture
Research Field:Architectural science and technology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in built environment and design
UTAS Author:Lock, A (Mr Andrew Lock)
UTAS Author:Holloway, D (Associate Professor Damien Holloway)
ID Code:104758
Year Published:2015
Deposited By:Engineering
Deposited On:2015-11-18
Last Modified:2017-08-08
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