Study On The Sound Absorption And Sound Insulation Performance Of Non Cylindrical Hole In The Composite Plate Grid Embedded With Iron Tailings Sand

With the rapid development of industry and the advancement of urbanization,the noise pollution has become more and more serious,especially in densely-populated areas,prosperous cities,and surrounding areas of expressway and railways,which has become hot topics on environmental management.Meanwhile,as the rapid development of high-rise buildings,it is required a higher standard on high strength light weight of separation wall and reduction of plot ratio.Therefore,the research and development of thin and lightweight building materials have become a hot research topic in the field of environmental noise control.It is of great significance to improve the plot ratio and reduce the load-carrying capacity of high-rise buildings that research,and production of the porous composite sound absorption and sound transmission loss materials has become a trend in the development of the new noise reduction materials.The porous structure is an effective way to make the material lighter,and can absorb sound more effectively with lower sound insulation.Meanwhile applying base material with high density to produce porous material can improve sound-insulated capability.Therefore,this thesis attempts to use the iron tailings sand as the filling material of the hollow plate to form a porous sandwich layer,and taking this topic as the research object in this thesis that we researched the calculation method and parameter influence law of non-cylindrical holes material about the sound absorption and insulation.A large amount of iron tailings sand have been abandoned,which has brought a lot of damage to the ecological environment.The research of this thesis is helpful to find a new way that the iron tailings sand is efficient and rational recycled.Firstly,in this thesis,the theoretical calculation model of cylindrical pore structure is based on the Biot theory.The structure of non-cylindrical holes can be regarded as a series of approximate cylindrical holes with different apertures.And the total transfer matrix is equal to the product of each layer transfer matrix.Based on this idea,the theoretical formula of the acoustic transfer matrix of the spherical holes perforated plate has been established.This thesis has compiled the exclusive numerical simulation program of the sound transfer matrix of the porous plate with a spherical holes compiled by using the MATLAB software platform and has discussed the optimal slicing number of the spherical holes in order to reduce the approximation error.Moreover,changing of the pore diameter,acoustic frequency,the thickness of material and the distances ofspherical center,it obtains the influence law of the parameters on the sound absorption coefficient and sound transmission loss,which can be the reference and basis of porous composite structure for the design.On the basis of the numerical simulation,this thesis makes use of the 3D printing technology to prepare the porous material of spherical holes whose thickness is 20 mm.By comparing with the experimental results,the correctness of the transfer matrix for the spherical holes theoretical formula has been verified.Finally,the idea of the theory of spherical holes has been used to construct the transfer matrix of irregular holes for preliminary discussion the irregular holes formed by filling tailings sand and experimental testing the sound transmission loss performance of the porous material filled with tailings sand,which lays the foundation for further research.Some important results are as follows:(1)The numerical simulation results by the formula based on the theory of the spherical holes transfer matrix are consistent with the experimental results.So,the transfer matrix of the spherical holes can be used for the design and calculation of the spherical porous acoustic material,and the idea can be extended to the theoretical study of irregular holes.(2)Based on the theory of the spherical holes transfer matrix,this thesis makes use of MATLAB software to simulate calculation.It is found that in random aperture the sound absorption coefficient of the spherical holes increases with the increase of the layer of slices and gradually tends to be stable.Therefore,this thesis searched from stable interval to find out the optimal slicing number which can not only meet the requirement of calculation accuracy but also reduce the computational burden of MATLAB computing software.Due to this,the relationship between the optimal slicing number and the diameter of the spherical holes can be used as reference for the design and calculation of the sound absorption and insulation of the spherical holes and irregular holes.(3)For the single layer of spherical holes,the sound absorption coefficient and the sound transmission loss decrease with the increase of pore size.And at the same pore size,the sound absorption coefficient and the sound transmission loss increase with the increase of the number of layers of holes.When the number of the holes layers is fixed,the smaller the aperture is,the greater the sound absorption coefficient and the sound transmission loss become.When the spherical holes are the same,the sound absorption coefficient and the transmission loss increases with the increase of distance from thecenter.(4)Iron tailings sand particles are assumed to be of the standard spherical type,so this thesis makes use of the conclusion of the spherical holes porous material and the idea of slicing to calculate and experimental test the porous material of iron tailings sand.And a good consistency has been shown in the result of comparison.(5)In this thesis,the expansion of spherical holes transfer matrix method is applied to irregular pores(such as cracks),and the result is feasible.This method has the value to further research.