摘要:
为获得理想吸声性能,提出了一种由多孔材料,微穿孔板及空气层构成的周期复合结构,并利用微穿孔板理论和等效流体多孔材料模型,结合等效电路法进行了分析。结果表明,复合结构显著增强了微穿孔板结构的中低频吸声性能,但其高频性能较单独多孔材料差;采用合适填充比例并联布置多种多孔材料,可适当调节复合结构的吸声性能。此外,周期复合结构的堆叠层数N≥1时,相对单层复合结构,中低频吸声带宽提升至少40%(≥380 Hz);相对多层微穿孔板结构,增大N对相应中低频吸声带宽提升不低于30%(≥300 Hz)。总体上,文中周期复合结构可显著增强传统微穿孔结构的中低频性能,是一种简单高效的中低频宽频降噪方案。
Abstract:
To get desired sound absorption,we proposed a novel periodic composite structure comprised of MicroPerforated Plate (MPP),porous material and air cavity.The composite structure is then solved using equivalent circuit model,with equivalent fluid porous model and Maa's theory.Distributed four-pole elements are used to handle structures which are not compact compared to the sound wavelength.The model procedures are validated and confirmed as satisfactory by published results and finite-element results.Analysis conducted on a single layer shows that,compared with traditional MPP,the porous addition here can increase the sound absorption in the low-to-medium frequency range;however,the advantage of porous materials in the high-frequency range is lost.Meanwhile,by parallel arranging the porous materials and controlling their filling ratios,the absorption curve of the composite structure can be tuned.As to the periodic composite structure,it is found that the influence of layer number N is mainly in the low-to-medium frequency range.When N varies,the half-absorption bandwidth increases over 40% (≥380 Hz) compared with a single layer.Compared with the multi-layered MPP,N=2 and N=4 produce an increase of bandwidth by 50% (≥400 Hz) and30% (≥300 Hz) respectively.As N increases,the sound absorption is better but the enhancement weakens as it tends to the limit of the composite structure.These results show the potential enhancements can be made to the traditional MPP,which can benefit the research on wideband noise reduction in the low-to-medium frequency range.
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