Kanfoud Jamil, Ali Hamdi Mohamed, Becot François-Xavier, Jaouen Luc
Laboratoire Roberval, Universite de Technologie de Compiegne, Centre de Recherche CRD338, Compiegne Cedex, France.
J Acoust Soc Am. 2009 Feb;125(2):863-72. doi: 10.1121/1.2973197.
During lift-off, space launchers are submitted to high-level of acoustic loads, which may damage sensitive equipments. A special acoustic absorber has been previously integrated inside the fairing of space launchers to protect the payload. A new research project has been launched to develop a low cost fairing acoustic protection system using optimized layers of porous materials covered by a thin layer of fabric. An analytical model is used for the analysis of acoustic wave propagation within the multilayer porous media. Results have been validated by impedance tube measurements. A parametric study has been conducted to determine optimal mechanical and acoustical properties of the acoustic protection under dimensional thickness constraints. The effect of the mounting conditions has been studied. Results reveal the importance of the lateral constraints on the absorption coefficient particularly in the low frequency range. A transmission study has been carried out, where the fairing structure has been simulated by a limp mass layer. The transmission loss and noise reduction factors have been computed using Biot's theory and the local acoustic impedance approximation to represent the porous layer effect. Comparisons between the two models show the frequency domains for which the local impedance model is valid.
在发射升空期间，太空发射器会受到高强度的声学载荷，这可能会损坏敏感设备。此前已在太空发射器的整流罩内集成了一种特殊的吸声器，以保护有效载荷。一个新的研究项目已经启动，旨在开发一种低成本的整流罩声学保护系统，该系统使用由薄织物层覆盖的优化多孔材料层。采用解析模型分析多层多孔介质中的声波传播。结果已通过阻抗管测量得到验证。进行了参数研究，以确定在尺寸厚度约束下声学保护的最佳机械和声学性能。研究了安装条件的影响。结果表明，横向约束对吸收系数非常重要，特别是在低频范围内。进行了传输研究，其中整流罩结构由柔性质量层模拟。使用比奥理论和局部声阻抗近似来表示多孔层效应，计算了传输损耗和降噪系数。两种模型之间的比较显示了局部阻抗模型有效的频域。
