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Lüke and power residue sequence diffusers

Dadiotis, K, Angus, JAS and Cox, TJ 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: Colleges and Schools > College of Science & Technology
    Colleges and Schools > College of Science & Technology > School of Computing, Science and Engineering
    Colleges and Schools > College of Science & Technology > School of Computing, Science and Engineering > Acoustics 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 15:58
    Last Modified: 20 Aug 2013 17:49
    URI: http://usir.salford.ac.uk/id/eprint/14626

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