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Ternary and quadriphase sequence diffusers

Angus, JAS, Cox, TJ and D'Antonio, P 2006, 'Ternary and quadriphase sequence diffusers' , The Journal of the Acoustical Society of America (JASA), 119 (1) , pp. 310-319.

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    Access Information: Copyright (2006) Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

    Abstract

    A room acoustic diffuser breaks up reflected wavefronts, and this can be achieved by presenting a spatially varying surface impedance. In hybrid surfaces, varying impedance is achieved by patches of absorption and reflection, giving reflection coefficients nominally of 0 and 1. These surfaces are hybrids, absorbing some of the incident sound while diffusing any reflected energy. A problem with planar hybrid surfaces is that specular energy is only removed by absorption. By exploiting interference, by reflecting waves out-of-phase with the specular energy, it is possible to diminish the specular energy further. This can be achieved by using a diffuser based on a ternary sequence that nominally has reflection coefficients of 0, -1, and +1. Ternary sequences are therefore a way of forming hybrid absorber-diffusers that achieve better scattering performance without additional absorption. This paper discusses methods for making ternary sequence diffusers, including giving sequence generation methods. It presents prediction results based on Fourier and boundary element method models to examine the performance. While ternary diffusers have better performance than unipolar binary diffusers at most frequencies, there are frequencies at which the performances are the same. This can be overcome by forming diffusers from four-level, quadriphase sequences.

    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 > School of the Built Environment
    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: H Kenna
    Date Deposited: 10 Sep 2007 11:28
    Last Modified: 20 Aug 2013 16:47
    URI: http://usir.salford.ac.uk/id/eprint/421

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