Direction control of a parametric speaker

In this study, we developed a parametric speaker system and analyzed the performance characteristics, wherein the direction of the audible sound wave can be electrically controlled. The system consists of an ultrasonic array transmitter with 144 ultrasonic transducer elements and field programmable gate array (FPGA) signal controllers. The phases of the amplitude-modulated signals for each transducer are controlled at 1 μs temporal resolution with ring buffers 511 μs in length. The direction can be controlled within a range of 15°, with a 2° resolution.