Development of Multi-way Parametric Array Loudspeaker Using Multiplexed Double Sideband Modulation
* Presenting author
Parametric array loudspeaker (PAL) can achieve a sharper directivity by utilizing ultrasonic wave than conventional dynamic loudspeakers. However, PAL has difficulty reproducing low-frequency sound because it utilizes demodulation of ultrasound in the air. We have proposed the multiplexed double sideband (M-DSB) modulation for PAL, which can enhance sound pressure level (SPL) by utilizing harmonic distortion in demodulation. However, in lower frequency, sound quality by PAL with M-DSB is still insufficient compared with one by dynamic loudspeakers. Therefore, in this paper, we develop a new multi-way PAL with combining software and hardware approaches, which can achieve both sharper directivity and powerful bass sound. Multi-way PAL consists of a tweeter PAL and woofer PALs, and each part is an aggregate of multiple ultrasonic transducers. Tweeter PAL employs single sideband (SSB) modulation, which gives low-distortion but low-SPL. Woofer PAL employs M-DSB modulation, which gives high-SPL but high-distortion. In order to achieve a flatter frequency response, we conducted preliminary experiments to determine both a suitable number of ultrasonic transducers and an optimized arrangement for tweeter PAL and woofer PALs. Finally, we confirmed the effectiveness of the proposed method through evaluation experiments.