A proposal of the directional speaker system based on the boundary surface control principle

Abstract

AbstractAccording to the boundary surface control principle, it is possible to reflect the flow of acoustic energy at a boundary if a boundary surface with impedance 0 can be formed by controlling the sound pressure and the particle velocity at an arbitrary position in space. If this principle is used in such a way that a boundary surface is formed only in the direction not intended for radiation of the sound, then a directional speaker system can be realized. In the conventional design method of the directional speaker array system, in order to achieve sharp directivity in the low frequencies, it is necessary to enlarge the array length. On the other hand, in our proposed system, it is easy to achieve sharp directivity in the low frequencies, since the boundary surface control principle can achieve high performance in the low frequencies. Moreover, by changing the control sound source spacing for each bandwidth, rather flat characteristics can be obtained over the entire control range. In this paper, the basic characteristics constituting guidelines for system design and the effect of control are confirmed by numerical calculations and experiments. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 88(2): 1–9, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20122