Ultrasound-Based Directional Sound System via Double Sideband Amplitude Modulation

Abstract

With unique advantages of reducing noise pollution, lengthening the propagation distance, directional sound system (DSS) is a novel technology to control sound directivity based on modulation algorithm. By using the double side band amplitude modulation (DSB-AM), we successfully design a DSS device and the experimental verification is conducted to evaluate the performance of the sound directivity with different ultrasonic array. The modulation and self-demodulation based on DSB-AM is simulated, which proves theoretically that the audible sound can be transmitted with ultrasound signal and recovered in air. The sound directivity influenced by operating frequency is simulated to determine carrier frequency. To attain optimal arrangement of the ultrasound array, the square and rectangular array is constructed in the simulation. We develop a DSS hardware configuration to investigate sound directivity of ultrasonic array. It proves that the envelope of the modulated signal is matched with the original audio signal when modulation factor m=0.5 is chosen, which can ensure the performance of transmitting sound. The sound directivity of ultrasonic array is evaluated qualitatively and quantitatively. The experiments show that the 7×7 array has the better sound directivity than the rest of arrays, where the minimum emitting angle of main beam is produced. Sound directivity demonstration solidly verifies the superiority of 7×7 array in audible music propagation.