Simulation Study on Directional Dispersion of Strong Noise

In dealing with emergencies, strong noise can effectively disperse the unruly crowd gathered illegally. Matlab was used to select different ultrasonic frequencies and individual transducer diameters, respectively, to carry out directional simulation of noise propagation, comparative analysis, to determine the selection of ideal ultrasonic frequency and transducer size. The directional image simulations of noise dispersal were carried out by selecting different array spacing of the transducer planar array. The noise dispersing sound pressure level was calculated to verify the noise dispersing efficiency. The determined optimal combination is ultrasonic wave with frequency f=40kHz, and the directional dispersing module selects a 4×4 array with diameter D=51mm and spacing d1=d2=1.2D=61.2mm. Introduction When dealing with mass emergencies such as large-scale illegal assembly and violent disturbance, targeted attack with strong noise can disperse effective targets without excessive harm to human body, and at the same time, it can produce ideal dispersing effect. However, the sound wave emitted by traditional loudspeaker is omnidirectional propagation, so it is difficult to produce audible noise with high directivity propagation and cannot achieve directional dispersing. Therefore, how to concentrate omnidirectional propagation noise in a specific direction domain and make it better directional propagation becomes the key link for the effective realization of directional dispersing of strong noise. Principle of Noise Dissipation System [1] Based on the principle of directional audio system, noise signal is transmitted by digital signal processor (DSP) loaded on ultrasonic signal. Because the acoustic attenuation coefficient is proportional to the second power of frequency, the ultrasonic waves and harmonics of higher frequency will be quickly absorbed by the air. The attack noise in the audible range is controlled to continue directional propagation in a certain area of space, and so the directional dissipation of noise can be achieved. The directivity of strong noise propagation is mainly realized by transducer. The sound pressure level of a single transducer is relatively small, and the directional propagation ability of the modulated noise is limited, so it is difficult to achieve effective dispersal effect. So the transducer should be formed into a plane array to improve the sound pressure level and propagation directivity of dispersal noise. Therefore, the directional dispersion effect of strong noise on living targets, will be determined by the parameters of a single transducer and a planar array. How to determine the size and other parameters of the transducer, how to make the planar array of the transducers give full play to the dispersing efficiency, and to give consideration to the size and structure limitations of the equipment and its own economic requirements, These are the primary problems to be solved in the research and development of noise dispersing equipment. Simulation Analysis of Noise Dissipation Directivity The parameters of the transducer and its array and the frequency of the ultrasonic wave all directly affect the directivity of noise propagation. The influence of transducer size, array spacing and array number on ultrasonic wave propagation directivity can be analyzed through simulation comparison, International Conference on Modeling, Analysis, Simulation Technologies and Applications (MASTA 2019) Copyright © 2019, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Intelligent Systems Research, volume 168