Sound-power visualization system for real-world interaction based on ultrasonic power transmission

We propose a sound-power visualization system that uses ultrasonic power transmission to assist in the direct physical interaction between users and a sound. For the ultrasonic power transmission, we develop a novel receiving unit that extracts electrical power from the ultrasonic sound propagated through the air using the piezoelectric effect. The extracted electrical power is used to drive various devices and actuators such as LEDs, motors, and loudspeakers. We design the receiving unit for the proposed sound-power visualization system named the Visualization System for Interaction with Transmitted Audio signals (VITA). In the VITA, 144 LEDs, which react to the sound emanating from a parametric loudspeaker, are arranged in a given space; this arrangement is used to provide a visual feedback to indicate the path of the sound. The feedback helps a user to manipulate the sound easily and directly and enables an interaction to be established between the user and the acoustical environment. With our proposed receiving unit, not all the LEDs need to be wired individually. We develop a system to visualize the sound field created in space and evaluate the established interaction and the performance of the sound-to-power transformation through demonstration and experiments. We also present a detailed evaluation of two circuits of the receiving unit that are used to turn on the LEDs and make the sound path visible up to a distance of 5 meters. One of the circuits has a narrow directivity of reception of less than 10°. The other has a wide directivity of reception of 25° and a high efficiency of transformation of ultrasonic sound to electrical power.