Sound focusing technology using parametric effect with beat signal
L. Ishimaru, R. Hyoudou · 2003
The purpose of this research is to focus sound into an arbitrary point, so that only a specific person can hear the information. We propose a new sound focusing method that uses a parametric effect by 2 kinds of ultrasonic speakers. From one speaker, ultrasonics are transmitted as carriers. From the other speaker, ultrasonics including audible sound by balanced modulation are transmitted. In the area where the 2 kinds of signal intersect, the ultrasonics are modulated like amplitude modulation by a beat signal. Also, by the parametric effect, audible sound is demodulated in air. So, only the person who stands around the intersection point can hear the sound. In this paper, we discuss the principle of the proposed method and experimental results.