Sound quality improvement based on weighted AM/FM modulations for parametric loudspeaker

Abstract

A parametric loudspeaker has high-directivity, and it utilizes a modulated wave that is designed by modulating an ultrasound wave with an audible sound wave. The conventional modulation methods, amplitude modulation (AM) and frequency modulation (FM), have been proposed. Furthermore, an AM/FM method has been proposed that can improve the sound pressure level (SPL). However, its sound quality is inferior to the AM method. The AM/FM method utilizes constant modulation parameters in all frequency bands. However, the power of audible sound demodulated by AM and FM modulations is different at each frequency band. Therefore, we propose a new AM/FM method that utilizes the weighted modulation parameters in each frequency band and can improve the sound quality. The proposed method has comparable sound quality to the AM method and a comparable SPL to the FM method. In this proposed method, we divided all frequency bands into three frequency bands and utilized the optimum weighted modulation parameters in the three...