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Development of a 2D boundary element method to model Schroeder acoustic diffusers


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Lock, AJ 2014 , 'Development of a 2D boundary element method to model Schroeder acoustic diffusers', Honours thesis, University of Tasmania.

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Acoustic diffusers are used in the treatment of critical listening environments,
and their performance is efficiently predicted by the Boundary Element Method
(BEM). Schroeder diffusers are highly effective due to diffusion lobes produced
by phase delays from different depth wells. The initial aim of this work was
to further develop and optimise a 2D BEM code by Rocchi & Smith (2013) for
modelling Schroeder diffusers, through improved computation methods and algorithms.
In particular, an analytical integral of the Green’s function for diagonal
matrix elements was implemented, and the numerical integration methods for all
other elements was refined. Computation time decreased by a factor of 50, and
average error for the test case of an infinite cylinder reduced by a factor or 200.
Intelligent discretisation methods also reduced the number of elements needed for
accurate results. The performance of Quadratic Residue Diffusers (QRDs) and
QRD modifications was investigated, including the e↵ects of design dimensions,
acoustic field type and repeating periods. A systematic approach was used to
model the performance of over 40 common diffusers. The superior performance
of Quadratic Residue Diffusers (QRDs) with larger sequences was confirmed when
modelled in a plane wave acoustic field. However, the performance of QRDs with
large sequences decreased significantly when modelled in a point source acoustic
field. Preliminary tests of a novel fractal QRD design displayed promising results.

Item Type: Thesis - Honours
Authors/Creators:Lock, AJ
Keywords: Acoustics, Architectural Acoustics, Boundary Element Method, Acoustic Diffusers
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Copyright 2014 the author

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