Arrangement of control points for sound spot generation in the multi-point control method

Abstract

In this research, we considered control point arrangement by using small-scale linear loudspeaker array. The multi-point control method is proposed for sound reproduction in a limited area/direction. This method is based on boundary surface control principle. The desired signal is reproduced in the target point by the sound pressure control in the control points. According to the MINT (multiple-input/output theorem), the signal is reproduced with accuracy in the target point if the number of sound sources more than the number of control points exists. However, a lot of speakers make it difficult to use in real environment. Therefore, small-scale loudspeaker array is preferable. If the number of control points is greater than the number of sound sources, the filter coefficient is approximated by the least squares-method. This approximation affects the sound pressure suppression and sound quality depending on the arrangement of control point. We examined the number of control points arranged. The input signal is the speech signal that has 300-3400 Hz frequency band. We evaluated some arrangement pattern by sound pressure, SD (Spectral Distortion), and PESQ (Perceptual Evaluation of Speech Quality). As a result, good results were obtained than conventional arrangement.