Theoretical And Experimental Research On The Sound Absorption Performance Of Wedge

Wedge sound absorption structure has excellent sound absorption performance in low frequency compared to other sound absorption structures because of its characteristics of gradual impedance, and its frequency range of sound absorption can be widened by adding a cavity or fillings. Wedge is widely used in anechoic pools, large anechoic chambers and surface ships. The thesis intends to research the sound absorption performance of wedge containing a cavity which is applicable for sonar flat area of the submarine suffered from vertical incidence acoustic wave.Firstly, wedge contains a cavity and fashions the heterogeneous sound absorption structure whose impedance changes gradually. Based on non-uniform wave guide theory, the wedge structure is divided into sequence of layers; the equation of sound absorption coefficient and the corresponding MATLAB computing program are established.Secondly, the thesis calculates the sound absorption coefficient of wedge that contains a cavity and compares it with the acoustic sound performance of the traditional plate structure. The result indicates that the sound absorption performance of wedge that contains a cavity is better because of broad sound absorption frequency range and excellent sound absorption performance in low frequency.Thirdly, the thesis researches the influencing factors of wedge's sound absorption performance. The length of wedge, material dynamic mechanical parameters, the cavity in wedge and hydrostatic pressure are considered. Significant conclusions are got by a lot of calculations and provide valuable reference for engineering practice.Fourthly, the thesis optimizes the wedge's sound absorption performance with the optimization theory through altering the material dynamic mechanical parameters and the cavity. The single-variable and multivariable optimizations are applied to the material dynamic mechanical parameters separately and the optimized frequency response curves are obtained. The cavity optimization design is discussed on the assumption that the shape and the length of the cavity are known in advance, the optimization result of the parameter that decides the variety of the cavity is obtained.Lastly, the thesis studies the sound absorption performance of wedge through experiment; the dynamic mechanical parameters of material and sound absorption coefficient are separately tested. The thesis obtains material parameters in a broad range under a certain temperature by using experimental result of material dynamic mechanical parameters in a frequency band under different temperatures. The results of sound absorption coefficient of wedge calculated in the thesis are compared with actual measured data, and the result indicates that the method adopted in this thesis is feasible.