Evaluation on multichannel surround sound system with parametric loudspeakers for sharpness of sound images

Recently, multichannel surround sound systems have been proposed to realize the sound field with high presence using multiple loudspeakers. The sound images of audio objects can be decomposed into point-like sources and diffused sources for effective and accurate audio synthesis. However, the perceived sound images lack sharpness due to the reverberation nature of the room. This drawback may cause poor synthesis of point-like sources. Then, we focus on a parametric array loudspeaker (PAL) which can achieve sharper directivity by the straightness of ultrasound. A PAL can reproduce sharper sound image because it has lower reverberation compared with conventional loudspeaker. Then the stereo sound system with two PALs had been proposed. In conventional researches, it is revealed that the system with PALs can achieve more accurate sound localization than the system with conventional loudspeakers in both horizontal and vertical planes. However, there are insufficient studies not only for using a multichannel surround sound system with PALs, but also for evaluating the sharpness of sound image. In this paper, we propose a multichannel surround sound system with PALs and investigate the sharpness of sound images. We evaluate the sharpness of them by objective and subjective evaluation when producing them at vertical plane.