Research On Sound Absorption And Scattering Characteristics Of Acoustic Coatings With Cavities

The acoustic coating is an important part of the submarine’s acoustic stealth technology.The cavity cover is an important model in practical engineering.It studies the propagation law of sound waves,analyzes the sound absorption performance and the intensity of the target,which is of great academic value and engineering significance.Through the calculation of the sound propagation and the material and structural parameters in the structure of the basic homogeneous layer and the cavity cover,the size and configuration of the cavity are optimized to form a complete processing framework,which can provide practical acoustic structure design certain reference.First,the sound absorption performance of a homogeneous multilayer structure is discussed.The theoretical derivation adopts the continuous relationship between the solid medium layers,establishes the transfer matrix,and solves the reflection and sound absorption coefficients.The results are compared with the calculation results of COMSOL simulation software to verify the validity of the theoretical method.At the same time,the analysis of the parameters affecting the rubber-steel layer structure shows that the increase of the sound wave incident angle and the thickness of the rubber sound-absorbing layer can improve the lowfrequency sound absorption performance within a certain range.The steel-water-steel multilayer backing layer is more likely to form standing wave resonance,which increases the peak and valley values of the reflection and sound absorption curves.Secondly,the sound absorption performance of the covering layer with cavity is studied.The layered gradient equivalent method is used to analyze a single cylindrical cavity that is periodically arranged.The gradient cavity is decomposed into a plurality of uniform cylindrical cavities.The governing equation of a single cylindrical cavity unit is used to obtain the axial equivalent complex wave number.Find the sound absorption coefficient.Compared with COMSOL simulation results,the validity of the theoretical method is verified.The analysis of the sound absorption performance of different cavity types shows that the peak of sound absorption is mainly affected by the axial vibration and cavity resonance of the overall structure.The value of the aperture ratio remains the same,and the sound absorption coefficient is also the same.Hydrostatic pressure makes the compression and deformation of the acoustic cover layer and cavity in the axial direction obvious,and the peak frequency of the sound absorption coefficient increases at high frequencies.Next,the homogenization equivalent of the cavity cover layer and the target strength calculation when laying on the shell structure are considered.The main material parameters of the homogeneous layer after the equivalent are obtained by the inversion of the genetic algorithm,and the reflection coefficients of the two before and after the equivalent are compared to verify the validity.On this basis,the equivalent homogeneous layer is applied to infinite and finite cylindrical shells and conical-cylindrical-spherical composite shells to calculate the acoustic target strength of the structure.The research shows that it is more accurate to calculate the target strength by using the equivalent uniform layer instead of the complex cavity layer,which has a significant advantage in computational efficiency compared with the refined modeling before equivalent.Finally,the optimization module in COMSOL is used to calculate the average value of the sound absorption coefficient of the cavity covering layer in the frequency band as the objective function,and to optimize the size and shape of the cavity structure in the covering layer,which effectively improves the low-frequency and broadband sound absorption performance.