【作者】 钱玉洁；

【导师】 孔德义；

【作者基本信息】 中国科学技术大学 ， 检测技术与自动化装置， 2014， 博士

【摘要】 微穿孔板(Micro-perforated panel, MPP)吸声体由我国著名声学专家马大猷教授于1975年提出,并建立了相关理论模型,称为马氏理论模型。微穿孔板吸声体自提出以来,就以其坚固、质轻、耐蚀和环境友好等诸多优点,被广泛应用于建筑物、船舶、飞机、消声器等众多领域,被誉为21世纪可以替代传统多孔吸声材料的最具吸引力的新一代吸声材料。然而,传统单层微穿孔板吸声体的一个显著缺点是吸声带宽较窄,一般为1-2个倍频程,作为一个通用的吸声结构这是远远不够的。此外,由于安装空间的严格限制,许多噪声控制问题都要求薄的降噪结构。因此,如何在不增加吸声体厚度的情况下拓宽单层微穿孔板吸声体的吸声带宽是目前的一个研究热点。本文重点围绕如何拓宽单层微穿孔板吸声体的吸声带宽,开发薄降噪结构展开相关研究。主要的研究内容包括以下几个方面：1.微穿孔板吸声体的吸声特性由其结构参数决定,如穿孔直径、板厚、穿孔率和空腔深度。本文通过MATLAB数值仿真对微穿孔板吸声体的吸声特性进行了参数化研究,得到了各结构参数与其吸声特性相互影响的规律。在充分理解微穿孔板吸声体吸声特性随其结构参数变化规律的基础上,设计了基于C++的面向微穿孔板吸声结构和吸声特性混合设计的软件平台,与以往微穿孔板吸声体设计平台不同,此平台综合考虑了结构参数和吸声特性参数两方面的限制,在实现微穿孔板吸声体按需设计的同时可兼顾最大吸声系数与吸收带宽之间的相互制约关系,提供满足混合设计要求的优化结构参数组合。2.实验探讨了超微孔微穿孔板吸声体的吸声性能。马氏理论模型预测穿孔直径小于100um的超微孔微穿孔板吸声体可达到单层微穿孔板吸声体的吸声带宽极限,但限于传统加工工艺如机械钻孔、针刺等对超微孔的加工难度,超微孔微穿孔板吸声体一直鲜见报道。本文对超微孔微穿孔板的加工工艺进行了探索研究,应用微机电系统(Micro-electronic Mechanical Systems, MEMS)工艺制作了超微孔微穿孔板。任何加工工艺都存在加工误差,对于传统的大孔径微穿孔板吸声体,数微米的加工误差基本可以忽略,然而对于孔径小于100um的超微孔微穿孔板,加工误差的影响可能不可忽略。本文建立了计及加工误差的MPP理论分析模型,率先从理论上探讨了加工误差对超微孔微穿孔板吸声体吸声性能以及马氏理论模型关于超微孔微穿孔板吸声体适用性的影响,数值仿真结果表明一定范围内的加工误差不影响超微孔微穿孔板吸声体的吸声性能以及马氏理论对其吸声性能预测的准确性(最大预测误差仍在6%以内)。最后,在驻波管中使用驻波比法测量得到超微孔微穿孔板吸声体的垂直入射吸声系数,实验验证了马氏理论模型关于单层微穿孔板吸声体带宽极限的理论预测以及计及加工误差的MPP理论分析模型关于加工误差对超微孔微穿孔板吸声体吸声性能影响得出的结论。3.理论与实验研究了多孔径微穿孔板吸声结构。基于MEMS工艺制作的超微孔微穿孔板吸声体可达到单层微穿孔板吸声体的带宽极限,且体积小,对有限吸声空间的降噪问题具有巨大吸引力,但随着孔径的减小,其吸声频带将移向高频,因而低频吸声性能变差,不利于中低频的降噪需求,且其制作成本相对于普通微穿孔板也较高。多孔径微穿孔板吸声结构具有优异的中低频吸声性能,其结构参数经过适当的设计可达到与多层MPP相当的吸声效果,且多孔径微穿孔板吸声结构更薄,适宜于狭小空间的降噪需求,不需要采用超微孔,制作成本较低。然而,多孔径微穿孔板吸声结构缺乏系统理论模型,因而无法对其吸声性能进行理论预测进而实现按需设计。本文基于体积流连续的原理,推导得到了声波垂直入射条件下多孔径微穿孔板吸声结构垂直入射吸声系数的理论计算公式,探讨了不同孔径微孔的排列及空腔中的隔板对多孔径微穿孔板吸声结构吸声性能的影响,最后通过实验验证了该理论模型的有效性,奠定了多孔径微穿孔板吸声结构的理论基础。4.相对于传统单层微穿孔板吸声体,多孔径微穿孔板吸声结构引入了更多的可变结构参数,大大增加了其设计复杂性,限制了其在实际降噪问题中的应用。为克服这一问题,本文提出了应用多种群遗传算法对多孔径微穿孔板吸声结构进行优化设计,在加工工艺允许的条件范围内,寻找最佳的参数组合,使其在设定的频带范围内平均吸声系数最高,达到宽频带高吸收的效果。最后,对该算法的有效性进行了实验验证,结果表明多种群遗传算法可作为一种直接、快速、高效的优化工具实现多孔径微穿孔板吸声结构的优化设计。更多还原

【Abstract】 Micro-perforated panel (MPP) absorber was first proposed by professor Maa D-Y in1975, and in the meanwhile its basic theoretical model was built which was called Maa’s theoretical model. Since Maa’s pioneering works, MPP absorber has been successfully applied in a lot of fields, such as buildings, ships, airplanes, mufflers and so on, for it is sturdy, lightweight, erosion-resisting and environmentally friendly compared with the traditional porous sound-absorbing materials and ordinary perforated panel absorbers, which makes it offers an outstanding alternative to the traditional porous materials and is regarded as promising as a basis for the next-generation of sound-absorbing materials.However, as a resonant sound absorbing structure, an obvious disadvantage of traditional single-layer MPP absorbers is that they are effective only in a narrow sound absorption band around their respective resonance frequencies, usually1-2octaves, which preventing them becoming general sound absorbers for a practical application. In addition, due to the limitations for installation space, many noise control issues require small-size noise-reducing structures. Thus, how to broaden the sound absorption bandwidth of single-layer MPP absorbers without increasing the thickness becomes the main focus of current research.In this paper, in order to develop small-size noise-reducing structures, the author has started a relevant research on how to widen the sound absorption bandwidth of single-layer MPP absorbers and has made many useful results.The main contents of study in this paper are as follows:Firstly, sound absorption characteristics of an MPP absorber is determined by its structural parameters such as the perforation diameter, the panel thickness, the perforation ratio and the depth of the air cavity. The influence rule of the variation of the structural parameters on the absorption performance has been studied through numerical simulation with MATLAB software. On the basis of full understanding of the influence rule of the structural parameters on the sound absorption performance, from the perspective of hybrid design of micro-perforated panel absorption structure based on the structure parameters and absorption characteristic, a software platform is developed by the object-oriented programing language C++. It is different from the previous design method by taking restrictions of both structure parameters and absorption characteristic parameters into consideration and balancing the restriction relationship between maximum absorption coefficient and absorption bandwidth of micro-perforated panel absorption structure according to the practical application, aiming at obtaining more satisfactory absorption curve. This platform will offer a set of optimal structure parameters that meet requirements of hybrid design.Secondly, micro-perforated panel absorbers with ultra-micro perforations, namely ultra micro-perforated panel absorbers (ultra MPP absorbers), are experimentally studied in this paper. Although Maa D-Y pointed out that the absorption bandwidth limits of a single-layer MPP absorber can be obtained by reducing the perforation diameter to less than100um, however, it’s difficult for traditional processing technology such as machining punching and needling skills to fabricate such small perforations, therefore MPPs with ultra-micro perforations have seldom been reported yet. This paper conducts an exploratory study of the processing technologies of ultra MPPs, and their trial production based on micro-electronic mechanical systems (MEMS) is carried out. Actually, the machining error exists in any processing technologies. For the traditional MPP absorbers with large perforations, the machining error range that is as large as several micrometers may has little or no effects on the sound absorption performance, but it could not be neglected for ultra MPPs. The theoretical analysis model of MPP absorbers on considering the effect of machining error is set up, and the effects of machining error on the absorption performance of ultra MPP absorbers and the accuracy of Maa’s theory for them are discussed. Results show that the measurements and the predictions calculated by the theoretical analysis model on considering the effect of machining error compare well with the calculations based on Maa’s theory with the maximum error being less than6%, which indicates that Maa’s theory is still available on considering the effect of machining error and the machining error within a certain range does not affect the sound absorption performance of ultra MPP absorbers. In addition, the limitation of Maa’s theory for machining error is discussed through numerical simulation, results reveal that it depends on the hole size of MPPs with ultra-micro orifices. Finally, the measurement of the normal sound absorption coefficients is carried out in impedance tube using standing wave ratio method and all the conclusions drawn above are experimentally validated.Thirdly, multi-size micro-perforated panel absorbers are theoretically and experimentally investigated. Ultra MPP absorber are of great potential to achieve the absorption bandwidth limits of single-layer MPP absorbers and with small size which make it strongly attractive to narrow space, however, its absorption band is shifted to high frequency as the perforation diameter decreases which will result a performance degradation in low frequency range. Moreover, ultra MPP absorbers have relatively high production cost compared with ordinary MPP absorbers with large size perforations. Therefore ultra MPP bsorbers are not suitable for reducing the low-frequency noise. Multi-size MPP absorber has the same absorption effect as multi-layer MPP absorbers provided that its structural parameters are proper designed and with thinner thickness. Since without using ultra micro-holes, multi-size MPP absorber is low-cost. All these advantages make it especially suitable for applications in the narrow space. However, due to the lack of theoretical model, it can not realize the needed design of multi-size MPP absorbers through theoretical analysis. Based on the flow continuity of air on both sides of MPP, the calculation of sound absorption coefficients of multi-size MPP absorbers is derived under normal incidence condition, and the effects of holes arrangements and the partition panels in the cavity on the sound absorption characteristics are discussed. Ultimately, the validity of the theoretical model is verified through experiments.Fourthly, multi-size MPP absorbers introduce more variable structure parameters compared to single-layer MPP absorbers with uniform-size holes, which greatly increases the design difficulty and thus limits their practical application. To overcome this problem, this work has applied the optimization design of multi-size MPP absorbers using multi-population generic algorithm (MPGA). It consists of finding the best combination of the structure parameters of a multi-size MPP absorber within given variation ranges that provides the maximum mean absorption for a specified frequency range. Ultimately, the correctness of the MPGA is experimentally validated. Results show that MPGA can be used as a straightforward, fast and effective technique to optimize multi-size MPP absorbers.更多还原