Evaluation of a multi-way parametric array loudspeaker based on multiplexed double sideband modulation

Parametric array loudspeakers (PALs) can achieve a sharper directivity than conventional electro-dynamic loudspeakers by utilizing ultrasonic waves. However, a PAL has difficulty reproducing low-frequency sounds because it utilizes the demodulation of ultrasound in the air. We proposed a multiplexed double sideband (M-DSB) modulation for a PAL, which can enhance the sound pressure level by utilizing harmonic distortion in demodulation. We also developed a multi-way PAL combining software and hardware approaches. Our multi-way PAL consists of a tweeter PAL (T-PAL) and woofer PALs (W-PALs), with different modulation methods and different numbers of ultrasonic transducers. In this paper, to evaluate the performance of the developed multi-way PAL, we carry out both objective and subjective experiments. In the objective experiments, the sound pressure level and frequency response are compared between target and non-target areas. In the subjective experiments, we evaluate the sound quality with sound sources of music and speech. From the experimental results, we confirmed the performance of our developed PAL in terms of frequency response, directivity, and sound quality.