Weighted double sideband modulation toward high quality audible sound on parametric loudspeaker

Recently, parametric loudspeakers have been utilized to reproduce an audible sound in a particular area by an ultrasound. However, parametric loudspeakers have lower sound quality than general electrodynamic loudspeakers because it is difficult to reproduce an audible sound at lower frequency. Moreover, the reproduced sound includes harmonic distortions causing deterioration of sound quality. Thus, in this paper, we attempt to improve sound quality of parametric loudspeakers. It depends on a modulation technique for designing the amplitude modulated wave. Therefore, we propose a new modulation method to reproduce audible sound with high quality. The proposed method controls a weight of double sidebands for reducing harmonic distortions at higher frequency and emphasizing power at lower frequency. We carried out evaluation experiments to confirm the effectiveness of the proposed method. The results confirmed that the proposed method could improve sound quality of parametric loudspeakers.