Acoustic Characteristics Of Micro-perforated Panel Absorbers With Parallelarranged Cavities Of Different Depths

Under the background of the development of large-scale and high-density cities,the problem of the impact of architectural acoustic environment on residents’ psychology and physiology is becoming more and more prominent.Among many noise pollution control methods,sound absorption is one of the widely and flexible control methods.The sound absorbers made of different materials are suitable for different occasions.The micro-perforated panel absorbers(MPAs)stand out from many sound absorption materials due to their advantages of pollution-free,moisture-proof and environment-friendly.However,the absorption bandwidth of MPAs is relatively narrow,and the existing methods of broadening the absorption band lead to the waste of space and are not flexible.In order to solve this problem,this paper has carried out the following research work.Firstly,a compound MPA backed with periodic cavities at different depths(PCD-MPA)is investigated.A theoretical prediction method for this kind of MPAs is proposed,and the corresponding finite element model is established to provide numerical verification.In addition,a full-scale model of PCD-MPA was made,and its random incident sound absorption coefficient is measured in the reverberation room as experimental verification.It is found that the sound absorption performance prediction method provided in this paper is accurate and reliable.Using this method,the sound absorption characteristics of PCD-MPA are deeply discussed.The results show that the number and position of the sound absorption peaks of PCD-MPA can be effectively controlled by adjusting the depth sequence of sub-cavities and the parameters of the microperforated panel,then the traditional absorption bandwidth of MPAs can be extended to four octaves.Secondly,from an application-oriented perspective,the design strategy of the compact PCD-MPA is discussed according to a certain parallel sub-cavities curling method,and the random incident sound absorption performance of this type of absorber is analyzed in detail.At the same time,the finite element model is built to validate the analytical method and to analyze the influence of the back-cavity structure parameters on the absorption characteristics of PCD-MPA.The results show that the proposed sub-cavity curling method does not significantly change the sound absorption performance;to a certain extent,the smaller sub-cavity width is beneficial for PCD-MPA to obtain a larger random incident sound absorption bandwidth.The results also show that the random incident sound absorption coefficient of PCD-MPA is not sensitive to the order of sub-cavity arrangement.Finally,based on the above research,a complete design method for PCD-MPA is proposed.The excellent absorption performance can be achieved in a limited space by designing multiple strictly coupled resonance frequency intervals.By optimizing the parameters of the micro-perforated panel,the depth sequence of the sub-cavities and the spatial folding method,a good sound absorber can be obtained in a limited geometric space.The proposed method of PCD-MPA provided in this paper can provide a useful reference for the design of broadband and efficient absorbers.