Directional Sound Radiation System Using a Large Planar Diaphragm Incorporating Multiple Vibrators

Yoko YAMAKATA  Michiaki KATSUMOTO  Toshiyuki KIMURA  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E92-A   No.6   pp.1399-1407
Publication Date: 2009/06/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E92.A.1399
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Engineering Acoustics
Keyword: 
audio reproducing device,  sound field reproduction,  directional sound radiation,  

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Summary: 
In this paper, we propose a new system for controlling radiated sound directivity. The proposed system artificially induces a bending vibration on a planar diaphragm by vibrating it artificially using multiple vibrators. Because the bending vibration in this case is determined by not one but all of the accelerated vibrations, the vibration of the diaphragm can be controlled by modulating the accelerated vibration waveforms relatively for each frequency. As a consequence, the directivity of the radiated sound is also varied. To investigate the feasibility of this system, we constructed a prototype that has for a diaphragm a circular plate-one of the most typical shapes considered for discussing plate vibration-and three vibrators. The measurement data showed visually that with this system, surface vibration and sound directivity change depending on the phases of the accelerated vibrations.