Zeinab Hojati - Department of Electrical Engineering, Amirkabir University of Technology
Seyed Mohammad Ahadi - Department of Electrical Engineering, Amirkabir University of Technology

Directional loudspeakers emit the audible sound with high directivity. These systems project the sound beam onto a target similar to a light beam emitted from a spotlight, while conven-tional sound systems are like light bulbs and fill the whole room with sound. In this paper, a directional loudspeaker system, named parametric array is analysed in detail and investigated by implementing and testing a hardware system. This type of system has less noise and more directivity among directional loudspeakers. Parametric loudspeakers produce audible sound by employing an array of ultrasound transducers which project a high intensity ultrasonic wave modulated by an audio signal. Due to an inherent nonlinear phenomenon of the propa-gation medium, the emitted signal self-demodulates on the transmission path and the audible sound regenerates. The implemented system, which is presented in this paper, uses DSB modulation and provides satisfying loudness. This system is tested and used in a restricted place to warn people entering without any permission. The angle directivity of 17 degrees is obtained due to the experiments

directional loudspeaker; parametric array; ultrasonic waves; self-demodulation