A Study Of Turned Double-layer Microperforated Panel And Its Sound Absorption Performance

The development of urbanization brings convenience to life but also brings many noise problems.However,thick acoustic materials are often required to achieve the ideal sound absorption performance,when absorbing low-to-mid frequency sound.Some fiberbased acoustic materials may also have potential health damage.As a green,lightweight and efficient resonant acoustic material,micro-perforated panel has very great advantages in the treatment of low-to-mid frequency sound,but the micro-perforated panel also has the problem of narrower sound absorption frequency band and longer back cavity required for absorbing low frequency noise,leading to a larger space occupation.The main work of this paper is to combine the concept of double-layer micro-perforated panel and folded back cavity to expand the width of the absorption band of micro-perforated panel in the low-to-mid frequency band,while keeping the acoustic structure thin and light in the direction of sound incident.The particle swarm optimization algorithm is used to realize the optimal design of the acoustic structure.For the limitations of the double-layer tandem microperforated panel in the application of low-to-mid frequency sound absorption engineering,this paper proposes a turned double-layer microperforated panel for low frequency sound absorption in enclosures with limited cavity space,in which the back-cavity space of a classical doublelayer microperforated panel is folded,which can effectively reduce the size of the backcavity in the direction of sound wave incidence while maintaining the efficient low-tomid frequency sound absorption performance of the double-layer microperforated panel.The theoretical model of the structure is established using the transfer matrix method,while the simulation model of the structure is built in the finite element software,and the parameters affecting the sound absorption effect of the structure are discussed.A smallsize sample is tested in the impedance tube,the experimental,simulation,and theoretical absorption curves are in good agreement,which further verify the excellent low-to-mid frequency absorption performance of the turned double-layer microperforated panel while keeping the structure thin and light.Further,a turned series-parallel combined double-layer micro-perforated panel absorber is proposed to further broaden the acoustic band of the structure.The theoretical model of the structure is established using equivalent electro-acoustic circuit,the real and imaginary parts of the acoustic impedance are analyzed to study the acoustic impedance conditions required to achieve perfect sound absorption.The simulation model of the structure is established by using finite element software to verify the validity of the theoretical calculation results,and the sound velocity distribution in the structure under plane wave incidence is simulated to study the broadband sound absorption mechanism of the structure.Finally,the structural parameters of the turned double-layer tandem microperforated panel sound absorption structure were optimized using particle swarm optimization algorithm,which effectively improved the sound absorption performance of the doublelayer microperforated panel.At the same time,experimental verification was carried out in the impedance tube.