直升机舱室声学超材料壁板的低频隔声性能分析

在直升机飞行过程中,旋翼、尾桨等噪声源在舱室内产生强烈的低频噪声,严重影响直升机的驾乘舒适性,长时间的噪声暴露会危及驾驶安全。直升机舱室常用的夹层壁板结构可有效隔绝中、高频噪声,但其低频隔声性能一般较弱。为有效降低直升机舱室内低频噪声,将局域共振型声学超材料与舱室夹层壁板结合,建立直升机舱室声学超材料壁板模型,采用有限元法分析平面波入射激励下声学超材料壁板的低频隔声性能,并探索局域振子质量、层间结构对隔声性能的影响规律。结果表明:相比敷设阻尼材料、布置动力吸振器等传统舱内降噪方法,声学超材料壁板能有效隔离低频噪声,形成380 Hz~620 Hz的宽低频带隙。增加局域振子质量可有效拓宽带隙宽度并增强带隙内声透射损失,增加纵向加强筋数目可增强结构整体刚度,使振动衰减。声学超材料内饰的引入可为解决直升机舱室低频噪声问题提供技术路线。

Low-frequency Sound Insulation Analysis of Acoustic Metamaterial Cabin Panels in a Helicopter

Rotors produce strong low-frequency noise in the cabins of helicopters during flight,which imperils the driving comfort and safety.Sandwich structures can effectively protect the cabin from medium-to-high frequency noise,but are weak for low-frequency noise insulation.This paper studies the low-frequency sound transmission through the sandwich structure with acoustic metamaterial panel for interior trim in order to enhance its low-frequency soundproofing of the helicopter cabin.The finite element method is used to calculate the sound transmission loss(STL)of the structure under the plane wave incidence.Particularly,the influences of local resonator mass and the interlayer’s structural stiffness of the STL are investigated.The results show that the acoustic metamaterial panel,owing to the formed broad bandgap in 380 Hz-620 Hz,can effectively increases the low-frequency STL of the sandwich structure.Furthermore,increasing local resonator mass can widen the bandgap and further enhance the overall STL.Increasing of the number of stiffeners can raise the overall stiffness of the structure and attenuate the vibration.The application of acoustic metamaterial interior trim in cabin panels provides a new way to tackle the problem of low-frequency noise inside the helicopter cabin.