Study On Sound Absorption Performance Of Micro Perforated Plate And Folded Channel Back Cavity Composite Structure

In the 21 st century,science,technology and industry are developing rapidly,which not only brings convenience to people’s life,but also produces a lot of pollution to the environment.Among them,noise pollution bears the brunt and has a great impact on our life.Therefore,it is imperative to find a structure that can effectively absorb noise.Micro perforated plate absorber（MPA）is a kind of sound absorption structure proposed in the last century,which is simple in design and easy to manufacture.The sound absorption coefficient is not limited by materials,but only related to its own parameters.However,MPA structure mainly absorbs high-frequency sound waves,and poor absorption ability of low-frequency sound waves.In order to solve these problems,based on the study of MPA structure,this paper studies the sound absorption performance of the composite sound absorber with the addition of flexural channel back cavity and porous material and the application of MPA composite structure.The specific research contents are as follows:Firstly,the structure model of MPA was established by simulation to study the sound absorption coefficient,the distribution of sound pressure and sound velocity at the peak frequency,and the variation relationship between the sound absorption body of micro-perforated plate and the thickness of micro-perforated plate,the diameter of small hole,the perforation rate and the cavity depth behind the plate,which was verified by experiment.Secondly,the partition structure in MPA cavity is modeled by thermal viscosity theory.The sound absorption coefficient of the structure is 0.87 and the distribution of sound pressure and sound velocity at the peak frequency is obtained by simulation.The effect of the baffler on the sound absorption performance of the structure is studied by adjusting the baffler parameters.The low-frequency sound absorption structure with 204Hz～270Hz sound absorption bandwidth and a peak sound absorption coefficient of 0.96 in the low-frequency stage was obtained by adding multiple bafflers into the MPA cavity,which was verified by experiments.Thirdly,based on the theory of inclined baffles,a bending channel structure was designed by adding several inclined baffles in MPA cavity,which can effectively absorb sound at 185Hz～248Hz and make the absorption coefficient reach 1.By means of simulation and experiment,the relationship between the structure parameters and the sound absorption performance of the structure is studied and analyzed.It is verified that MPA composite inclined diaphragm structure can effectively improve the sound absorption performance of MPA structure at low frequency.Finally,the broadband absorption of MPA structure is studied.By adding porous materials into the structure,the influence of porous materials on the sound absorption performance of MPA structure and MPA composite structure was studied.It is found that porous materials can effectively broaden the frequency band,which can make the effective sound absorption bandwidth of MPA increased to 504 Hz ～1342Hz.The sound absorption bandwidth of composite structure is also effectively improved near the absorption peak.The MPA composite diaphragm structure was combined to study the influence of different MPA composite structures on the performance of the sound absorber of the composite structure.The combined sound absorber structure can effectively absorb sound at the stage of 200Hz～335Hz,with the peak of sound absorption coefficient reaching 0.97,and can also effectively absorb sound in the range of 584Hz～1383Hz,with the peak of sound absorption coefficient reaching 0.97,which solves the problem of poor sound absorption capacity of MPA in the low frequency range.