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Journal of the Acoustical Society of America / Volume 131 / Issue 2 / JASA EXPRESS LETTERS

A selective array activation method for the generation of a focused source considering listening position

J. Acoust. Soc. Am. Volume 131, Issue 2, pp. EL156-EL162 (2012); (7 pages)

Min-Ho Song1, Jung-Woo Choi2, and Yang-Hann Kim2

1Graduate School of Culture Technology, Korea Advanced Institute of Science and Technology, Science Town, Daejeon, 305-701, Korea godspd@kaist.ac.kr
2Center for Noise and Vibration Control, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Science Town, Daejeon, 305-701, Korea khepera@kaist.ac.kr, yanghannkim@kaist.ac.kr

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A focused source can provide an auditory illusion of a virtual source placed between the loudspeaker array and the listener. When a focused source is generated by time-reversed acoustic focusing solution, its use as a virtual source is limited due to artifacts caused by convergent waves traveling towards the focusing point. This paper proposes an array activation method to reduce the artifacts for a selected listening point inside an array of arbitrary shape. Results show that energy of convergent waves can be reduced up to 60 dB for a large region including the selected listening point.

© 2012 Acoustical Society of America

Acknowledgment

This work was supported by the Ministry of Knowledge Economy grant funded by the Korea government (Grant No. 10037244), and the BK21 (Brain Korea 21) project initiated by the Ministry of Education, Science and Technology. The author would like to thank Jung-Min Lee and Dong-Soo Kang of NOVIC at KAIST for the computer simulation works.

Article Outline

  1. Introduction
  2. Problem definition
    1. Time-reversed acoustic focusing solution
    2. The causality artifacts
    3. Measure of the causality artifacts (Ref. )
  3. Reducing of the causality artifacts
    1. Array selection based on the criterion Δ tth
    2. Reducing of non-causal waves using angular weight
  4. Examples
    1. Linear array
    2. Circular array
  5. Conclusion

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KEYWORDS and PACS

Keywords

acoustic arrays, acoustic focusing, acoustic radiators, hearing, loudspeakers

PACS

  • 43.60.Tj

    Wave front reconstruction, acoustic time-reversal, and phase conjugation

  • 43.66.Qp

    Localization of sound sources

ARTICLE DATA

History
Received 21 Nov 2011
Accepted 04 Jan 2012
Published online 26 Jan 2012
Digital Object Identifier
http://dx.doi.org/10.1121/1.3679006

PUBLICATION DATA

ISSN

0001-4966 (print)  

Publisher

$abstract.society.value is a Member of CrossRef Acoustical Society of America

  1. E.N.G. Verheijen, “Sound reproduction by wave field synthesis,” Ph.D. thesis, Delft University of Technology (1997).
  2. J. Ahrens and S. Spors, “Focusing of virtual sound sources in higher order ambisonics,” in Proceedings of the 124th Audio Engineering Society Convention, preprint 7378, Amsterdam, The Netherlands (May 2008).
  3. S. Spors, H. Wierstorf, M. Geier, and J. Ahrens, “Physical and perceptual properties of focused sources in Wave Field Synthesis,” in Proceedings of the 127th Audio Engineering Society Convention, preprint 7914, New York, USA (October 2009).
  4. H. Wallach, E. B. Newman, and M. R. Rosenzweig, “The precedence effect in sound localization (tutorial reprint),” J. Audio Eng. Soc. 21(10), 817–826 (1973).
  5. J. Blauert, Spatial Hearing, revised edition (MIT Press, Cambridge, MA, 1983), pp. 201–222.
  6. S. Spors, “Extension of an analytic secondary source selection criterion for wave field synthesis, in Proceedings of the 123rd Audio Engineering Society Convention, preprint 7299, New York (October 2007).
  7. J. Ahrens and S. Spors, “Spatial encoding and decoding of focused virtual sound sources,” in Proceedings of the Ambisonics Symposium 2009, Graz, Austria (June 25–27, 2009).
  8. S. Yon, M. Tanter, and M. Fink, “Sound focusing in rooms: The time-reversal approach,” J. Acoust. Soc. Am 113(3), 1533–1543 (2003).
  9. J.-W. Choi and Y.-H. Kim, “Generation of the acoustically bright zone with an illuminated region using multiple sources,” J. Acoust. Soc. Am. 111(4), 1695–1700 (2002).
  10. M.-H. Song and Y.-H. Kim, “Acoustic measure of causality artifacts for generating focused source,” in Proceedings of the 43rd Audio Engineering Society International Conference, Pohang, Korea (Sept. 29–Oct. 1, 2011), available only on CD-ROM.

Figures (click on thumbnails to view enlargements)

FIG.1
(a) Illustration of the converging region and the diverging region when the focusing point is at F, using an 1D array. Dotted line denotes the causality artifacts. (b) Schematic of control zone including a focusing point (F), listening position (L), and control sources (S).

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FIG.2
(a) Time domain signal at the listening position. (b) Array selection method using criterion based on the threshold of arrival time difference which is dependent on a listener.

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FIG.3
(Color online) Distribution of energy ratio Q comparing typical time-reversed solution with modified angular weight solution. A linear array (21 monopole sources, total aperture size: 2 m) was used for (a), (b). A focusing point was chosen at (0,−0.5 m). A threshold arrival time Δtth was chosen as 1 ms and the dark area denotes the area with Q less than 0 dB. For cases (c), (d), (e), and (f), a circular array with 70 monopoles were used. White dots indicate the location of control sources, L and F denote the target listening position and the focusing point.

FIG.3 Download High Resolution Image (.zip file) | Export Figure to PowerPoint



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