A Method for Changing Sound‐Image Position Using the Linear Loudspeaker Array and Two‐Dimensional FIR Digital Filter
Kiyoshi Nishikawa, Tetsuya Yokoyama, Mikiko Miyagishi · Electronics and Communications in Japan (Part III Fundamental Electronic Science) · 2002
Abstract In this paper, the problem of sound‐image control is considered as that of wave front shape of the acoustic beam radiated from a speaker array. A method is proposed for realizing the sound‐image control in an acoustic beam by providing the necessary delay characteristics to a two‐dimensional FIR filter as the group delay. The filter design is carried out by means of a two‐dimensional Fourier series approximation in which the fan‐shaped passband amplitude is specified for formation of the radiation pattern in addition to the required group delay. It is found that the degree of approximation in the filter design can be improved substantially by making the radius of the circle set for modification infinite. Further, the center of the circle forms a focal point as in an optical system and this point becomes a virtual sound source and hence the position of the sound image. The wave is expanding in a manner of concentric circles from this point. The width of the acoustic beam generated from this sound image is determined by the spread of the speaker array and the position of the sound image. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 85(4): 20–31, 2002