Simulation Study On Sound Absorbing Body Of Perforated Plate With Ultrathin Resonant Cavity

The resonance sound absorber of perforated plate is one kind of resonance sound absorbing structure that is widely concerned by scientists.The sound absorber of perforated plate is one kind of acoustic metamaterial,which is favored by many scholars because of its strong,environmentally friendly,and corrosion-resistant.However,this conventional sound absorbing structure of perforated plate has certain defects,the most obvious is that the structural size is still large,which limits the development of this structure in the field of small-sized sound absorption.The sound absorption bandwidth of the sound absorber is relatively narrow.In the daily production life,we want to use the sound absorption equipment as small as possible,and the sound absorption effect must meet the noise reduction requirements.Therefore,it is a research hotspot in the field to study perforated plate resonant sound absorbers with small size and good sound absorption effect.This article will explore an improved structure based on this traditional perforated plate resonant sound absorber—a perforated plate absorber with an ultrathin resonator backed.The size of the resonator of this improved structure will be under the millimeter.There are three points in this paper:First,we studied and analyzed the perforated plate absorbers with ultra-thin planar cavities.From the analysis of the simulation results of this structure,we determined that the perforated plate resonance absorbers with smaller dimensions have better sound absorption.With the increase of the thickness of the ultra-thin planar cavity,the effective sound absorption coefficient of the structure will increase first and then decrease,and the maximum sound absorption coefficient can reach about 93%.As the radius of perforation increases within a certain range,the sound absorption coefficient in the low-frequency resonance mode also increases first and then decreases,and there is no obvious law for the influence of high-frequency resonance in this process.The maximum sound absorption coefficient is as high as 99%.Second,in the analysis of the previous structure,we found that when the thickness of the ultrathin planar cavity is less than a certain value,the sound absorption coefficient of the structure will deteriorate sharply.Therefore,for this problem,we propose the first optimization scheme—the perforated plate absorber with an ultra-thin “stepped” cavity.The structure of the ultra-thin "stepped" cavity of the backing has a nearly 40% improvement in the maximum sound absorption coefficient relative to the structure of the ultra-thin planar cavity of the backing,and the maximum sound absorption coefficient is also about 95%.The sound absorption bandwidth has also expanded to nearly 0.8 kHz.As the proportion of the relatively thin cavity portion in the ultra-thin "stepped" cavity gradually becomes larger,the sound absorption coefficient of the structure tends to become larger,and the resonance frequency in the high-frequency resonance mode gradually moves to the low frequency direction,while the resonant frequency in the low frequency resonant mode has hardly been affected.Thirdly,on the basis of the perforated plate sound absorber backed by the ultra-thin planar cavity,we also proposed a second improvement scheme-a perforated plate sound absorber backed by an ultra-thin "square-well" cavity.We compared the sound absorption coefficient of this structure with the sound absorption coefficient of the structure under the ultra-thin planar cavity of the backing,which confirmed that the structure has a 25% improvement in the sound absorption coefficient of the original structure.The maximum sound absorption coefficient has reached 99.8%(perfect sound absorption),and the effective sound absorption bandwidth has expanded to a maximum of 1.5 kHz.At the same time,as the proportion of the ultra-thin "well cavity" in the whole cavity gradually decreases,the sound absorption coefficient of the structure gradually increases,and the resonance frequency in the high-frequency resonance mode gradually moves toward the low frequency direction,and the resonance frequency in the low-frequency resonance mode is almost unaffected.