Development of Parametric Loudspeaker

Abstract

Based on nonlinear acoustic and acoustic signal processing theoretical analyses, we designed and implemented a directional sound projection (or parametric loudspeaker) system, known as the audio beam system (ABS). The prototyping of the parametric loudspeaker consists of three main components: a digital signal processor (DSP), amplifier, and ultrasound emitters. The programmable DSP is the main processing block of the parametric array that performs preprocessing, such as equalization, dynamic range control, carrier control, and our proposed modified amplitude modulation techniques. The special-designed class-D amplifier is used to adjust the voltage gain to drive an array of ultrasound emitters, which are made of lead zirconate titanate or polyvinylidene fluoride materials. Due to the nonlinear interaction of the air, directional audible sound will be generated at a targeted sweet spot. The ABS was recently installed in a gaming booth in the Fusionopolis, a research and development complex located at the One-North business park in Singapore. We used two ABS speakers (ultrasound emitters) to project directional binaural sound from a gaining console to the gamer standing in front of the gaming booth. This setup confines sound to a predetermined sound zone. A laser or LED device fitted to the ABS speakers can project a light beam with the same direction as the sound beam to indicate the sweet spot on the floor. The gamer within the zone can enjoy playing the game without disturbing the other visitors beyond the defined "tune-in" zone.