Lüke and power residue sequence diffusers

Dadiotis, K, Angus, JAS and Cox, TJ ORCID: https://orcid.org/0000-0002-4075-7564 2008, 'Lüke and power residue sequence diffusers' , The Journal of the Acoustical Society of America (JASA), 123 (4) , pp. 2035-2042.

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Abstract

Conventional Schroeder diffusers have been successfully used for many years. However, their frequency range is limited by the flat plate effect that occurs when all the wells radiate in phase. This occurs at harmonics of p times the design frequency f(0), where p is the small prime that is used to generate the structure. A typical diffuser, using p=7 and f(0)=500 Hz, has an upper frequency limit of only 3.5 kHz. Achieving a first flat plate frequency above 20 kHz requires a prime equal to at least 41 and results in diffusers that are too big to be practical in most applications. This paper suggests an alternative approach using number theoretic sequences that, although short in length, are based on large integers. Two new sequences, Type-II Luke and power residue, have this desired characteristic. They are investigated using both simple models and the more exact boundary element method. The results show the flat plate effect is moved to much higher frequencies as expected. For Luke sequences at certain frequencies, redirection rather than dispersion is achieved. Modulation techniques can be used to mitigate these problems. Power residue sequences perform the best, providing good diffusion and a flat plate frequency outside the audible range.

Item Type:	Article
Themes:	Subjects / Themes > Q Science > QC Physics > QC221-246 Acoustics - Sound Subjects outside of the University Themes
Schools:	Schools > School of Computing, Science and Engineering Schools > School of Computing, Science and Engineering > Salford Innovation Research Centre
Journal or Publication Title:	The Journal of the Acoustical Society of America (JASA)
Publisher:	Acoustical Society of America
Refereed:	Yes
ISSN:	0001-4966
Depositing User:	TJ Cox
Date Deposited:	13 Apr 2011 14:58
Last Modified:	16 Feb 2022 11:18
URI:	http://usir.salford.ac.uk/id/eprint/14626

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