Rubber Sound Shielding Performance

The effectiveness of the acoustic baffle is a determining factor in the maximum capability of a sonar system. Basically, the baffle is a structure, placed between an unwanted signal or noise source and a sensor, to shield the sensor from the unwanted source. To achieve an array gain consistent with the directivity index of the array, efficient baffle structures must be provided. A further purpose of the baffle is to provide a desired response character for the hydrophone array. Thus, the acoustic is a primary tool for underwater noise reduction and directivity pattern control in sonar arrays.The traditional baffle is made of low impedance material such as foams. It has high efficiency at low hydrostatic pressures. When the pressure increases, its validity gets worse. The speciality of low impedance material limits the application at high hydrostatic pressures.The performance of the baffle is affected by several factors, such as its density, its velocity of sound, its dimension and the medium around. Thus the design of the baffle is complex.Rubber has intensity, mechanical loss performance, flexibility and stability during wide range of temperature. It can be used to manufacture the acoustic baffle with cylindrical dust. As the speed of the shear wave of styrene-butadiene rubber (SBR) is lower than other rubbers, it is more suitable for the acoustic baffle material.Based on the theory of the traditional baffle, a pressure-release model is made with SBR. It has high efficiency throughout a broad range of incident acoustic frequencies and designed for use at high hydrostatic pressures on analyzing the dynamic mechanical performances.In this paper, three aspects of baffle have been studied emphatically with flexibility equation and analytic method. 1) The elementary material of baffle is tested, indicating the dynamic mechanical performances. 2) Rubber in the form of cylindrical duct is used as underwater acoustic reflection baffle, and its mechanism of the acoustic transmission in different mediums is described. The formula for calculating the main acousticperformances of baffle is derived by static approximation. 3) For an immersed baffle model, theoretical calculation and analysis have been carried out at different frequencies, giving baffle performance variation with loss factor, shear modulus as well as thickness of this kind of material.