耦合声阻抗在扩散吸声体设计中的应用研究

为解决小房间的音质设计问题,需要设计不同的扩散吸声体。利用共振吸声的边缘效应,通过不同共振频率的共振器耦合共振时的非线性声阻抗变化组合,形成既能高效吸声,又能均匀散射的声学界面。数值分析及实验结果表明,新型的扩散吸声体内部没有任何传统吸声材料的情况下,单位面积吸声量在中低频段可达1.3 m2,在高频段由于非线性声阻抗与共振器的辐射阻抗不匹配影响,相应吸声量降低到0.7 m2左右。耦合声阻抗的运用使得新型扩散吸声体吸声的效率高,频带宽,免去传统吸声材料的使用,在小房间的声学应用中具有突出的优势。     

大面积多周期伪随机序列扩散体群的一种优化布置方案

伪随机序列扩散体具有良好的扩散效果，但是大面积周期布置时会在扩散方向产生大量旁瓣。为了消除这些旁瓣，并得到符合使用者要求的扩散声压响应曲线，本文提出一种实现伪随机序列扩散体群大面积最佳布置方案的布置方法。     

伪随机扩散体的吸声性能及其应用

本文介绍伪随机扩散体吸声性能的应用，提出减少扩散体结构厚度的实用设计，并应用于剧场观众厅以减少混响时间．     

微穿孔板吸声体的研究进展

简述了马大猷教授的微穿孔板基本理论、微穿孔板吸声体在扩散声场以及在高声强环境下的理论要点。比较详细地讨论了30年来与马大猷教授所提理论相对应的实验研究结果及应用发展情况。基于马大猷教授的基本理论,提出了一种新的相关衍生结构——管束微穿孔板。对微穿孔板吸声体的发展趋势做了展望。表明:微穿孔板吸声体将成为新世纪的绿色理想吸声材料。     

微穿孔板复合对二次余数扩散结构扩散性能影响研究

扩散吸声结构(Diffsorber)能应用于室内外声品质的改善,具有很好的研究意义和应用前景。微穿孔复合QRD结构能显著提高低频吸声性能,但复合对扩散性能的影响未见报道。本论文对QRD结构及其与厚度为0.6mm,穿孔率为1%,2%,3%的微穿孔板复合结构的扩散性能进行测试,得出了相应的反射声能极坐标图和扩散系数。研究结果表明,微穿孔复合QRD结构在中低频特别在结构自身共振频率范围内具有良好的扩散性能,扩散系数在0.8到0.95之间,随着频率增加,复合结构的扩散性能有下降的趋势,同时由于微穿孔板的吸声性能,复合后结构的空间反射声能普遍降低5dB左右。     

混响室中扩散体的总面积和测得的吸声系数

一、引 言 按混响室法作吸声系数测量时,人们总是用在混响室内尽可能无规地悬挂扩散体的办法来获得必要的声扩散。大的弯曲平板就是常用的一种扩散体。过去认为,扩散体的总面积是一个非常重要的量,如太小,则由于扩散不足测得的吸声系数太低,如太大,吸声系数同样会偏低,因为混响过程主要由扩散体之间的多次声反射而不再由房间某个墙面的吸声系数决定。一般取扩散体总面积为地板面积的1.6倍。根据在欧洲和美国做的几次巡迴测量和最近的研     

微穿孔吸声体随机入射吸声性能

依据“扩散场内微穿孔板吸声特性的实验研究”一文初步实验结果,对微穿孔板吸声体在扩散场内吸声特性进行了进一步探讨。在穿孔板常数K值较大时,（K＞2）,发现扩散场吸声特性与垂直入射情况相似但移到较高频率范围,除主要吸声频带外,在较高频率由于余切函数的多支性,还有次吸声频带但影响较小．k值较小（K≤2）时,扩散声场吸声特性在高频段的次吸声频带越来越重要,逐渐成为吸声的重要因素,使微穿孔板吸声结构在三或四倍频程以上具有高吸声系数,增加了它的实用价值。文中对扩散场内微穿孔扳吸声性质的变化作了具体计算并作了解释．     

杭州电声厂混响室的声学设计和鉴测

使混响室获得扩散声场是声学设计中最主要的问题。在我国已建的混响室建筑中,虽然都做了各种为实现声扩散的努力,但能获得预期效果的不多,从而不得不追加扩散结构。电声厂混响室用不规则室形和球切面扩散结构相结合的方法,获得了良好声扩散效果。本文将着重介绍有关声扩散的设计,同时,对该混响室的声学设计和鉴测也作概要的叙述。     

水下微穿孔吸声体结构设计与试验研究

根据马大猷院士的微穿孔板(MPP)理论,提出在可设计的夹芯复合隐身结构的空腔中附加微穿孔板层的水下微穿孔吸声体。基于微穿孔板的精确计算理论及水下声隐身结构的特点,考虑空腔深度、穿孔板厚度、穿孔直径及穿孔率等对微穿孔板吸声性能的影响,对水下微穿孔吸声体进行了结构设计。利用脉冲声管法对水下微穿孔吸声体试样的吸声系数进行了测量,结果表明:水下微穿孔吸声体有效地拓宽了低频吸声频带,其微穿孔板结构参数的影响规律也与理论分析一致;对于多种吸声机理并存的水下微穿孔吸声体的空腔个数、形状及谐振特性等也是影响吸声性能的重要因素,在实际的工程应用中必须结合所关心的频带对水下微穿孔吸声体进行匹配优化设计。     

卫星平台高光谱复杂运动成像伪互相关退化仿真研究

针对具有推扫机制的狭缝体制成像光谱仪受卫星平台俯仰、侧滚、偏航等复杂运动的影响,导致光谱数据精度降低的问题,在成像光谱仪运动成像光谱微分动态成像退化仿真方法的基础上,提出基于点扩散矩阵的光谱退化理论。按照八邻域掺杂模型,考虑卫星平台运动的时变性,不同目标像元的点扩散矩阵不同,符合伪互相关运算的概念,因此提出运动成像的伪互相关光谱退化理论。其中,点扩散矩阵由星上POS数据运用微分像移理论计算八邻域掺杂像元的平均掺杂比得到,在用模拟POS数据曲线仿真计算点扩散矩阵时,发现依据掺杂影响的大小,点扩散矩阵可以简化以便减小运算量。明确阐述光谱运动成像的伪互相关退化理论的表述和计算方法,对退化仿真和计算的结果从图像维和光谱维分别进行了定性和定量的效果评价,并使用结构相似度参数展示了退化图像与原始图像的相似性。运动成像的伪互相关光谱退化理论完善了已有的基于卫星平台复杂运动的光谱数据退化问题,仿真结果表明此种退化理论完全适用于解决卫星平台复杂运动条件下的光谱数据退化问题。     

Enhancing the low frequency sound absorption of a perforated panel by parallel-arranged extended tubes

This paper is concerned with the use of a perforated panel with extended tubes (PPET) to improve the sound absorption confined to low frequencies. In comparison with a micro-perforated panel (MPP), the sound absorption can be significantly improved by using the PPET at the expense of the bandwidth of the sound absorption. A particular configuration combining four parallel-arranged PPETs with different cavities is introduced to achieve a wider bandwidth of the sound absorption at low frequencies. The analysis is extended to the combination of three parallel-arranged PPETs and a MPP to further increase the bandwidth of the sound absorption. A theoretical model is described to predict the sound absorption coefficient and the simulated annealing method is introduced to the proposed absorbers, allowing optimization of the overall performance. The theory with experimental validations demonstrates that the proposed configurations offer a potential improvement of more than one octave in the bandwidth of the sound absorption at low frequencies.     

高分子梯度溶液吸声机理的研究

制备了高分子均匀溶液和梯度溶液,并在声管中测试其声衰减性能.实验结果表明,高分子梯度溶液的声衰减效果明显优于(即大于)相应的均匀溶液的声衰减.根据连续分层介质中声波传播理论建立了计算高分子梯度溶液声衰减的数学模型.计算结果与实验结果一致.由实验和理论分析结果得出了高分子梯度溶液的梯度吸声机理,即多次反射、多次吸收,最终将声能转化为热能.     

Effect of a honeycomb on the sound absorption characteristics of panel-type absorbers

Panel-type sound absorbers are commonly used to absorb low-frequency sounds. Recently, a new type of panel/membrane absorbers has been proposed as a next-generation sound absorber free from environmental problems. On the other hand, it is known that placing a honeycomb structure behind a porous layer can improve sound absorption performance and a similar effect can be obtained for microperforated-panel absorbers. Herein, the sound absorption characteristics of a panel sound absorber with a honeycomb in its back cavity are theoretically analyzed. The numerical results are used to discuss the variations in the sound absorption characteristics due to the honeycomb as well as the mechanism for sound absorption.     

Theoretical analysis on sound absorption by pseudostochastic diffusors

I.IntroductionIn1979,M.R.S.h.o.der[1]pro-posedanewdesignofsounddiffusorwhoseperiodcomprisesNelements(slotsorwells,referedtoaschannelsinfol1owing)ofequalwidths.ThedepthsofchanneIsvaryaccordingtoapseu-dostochasticsequencewithinonepe-riod.Atypicalstructureofq1ladraticresiduediffusor(N=11)isi1IustratedinFig.1.BychoosingthedePtl1ofchannels,thescatteringcharacteristicsofthestructurecanbeoptirnizeds11chastodistributethescattereden(}rgyequalIyoveralloweddirections.In1992,K.Fuiwaraandothers['repo…     

Sound absorption of microperforated panel mounted with helmholtz resonators

Microperforated panel (MPP) absorbers have been widely used in noise reduction and are regarded as a promising alternative to the traditional porous materials. However, the absorption bandwidth of a single-layer MPP is insufficient to compete with the porous materials. In order to improve the sound absorption ability of the single-layer MPP, MPP mounted with Helmholtz resonators (MPPHR) is introduced. Based on the MPP, Helmholtz resonators theory and electro-acoustical equivalent circuit principle, sound absorption properties of MPPHR are studied. Simulation and experimental results show that MPPHR have two peak frequencies and one anti-resonant frequency. The low-frequency peak is dependent on the Helmholtz resonators, while the high frequency peak is close to the peak of the single-layer MPP. The low-frequency sound absorption peaks move to low frequency with the neck length and the volume of Helmholtz resonators increasing. The high-frequency sound absorption peaks move to high frequency with the volume of Helmholtz resonators cavity increasing. Multiple Helmholtz resonator parallel MPP structure can provide more sound absorption than single MPPHR at low frequency range due to the introduction of more additional sound absorption peaks.     

Experimental study on sound absorption performance of microperforated panel with membrane cell

Microperforated panel (MPP) absorbers have been widely used in noise reduction and are regarded as a promising alternative to the traditional porous materials. However, the absorption bandwidth of a single-layer MPP is insufficient to compete with the porous materials. In order to improve the sound absorption ability of the single-layer MPP, a composite MPP sound absorber with membrane cells (MPPM) is introduced. Sound absorption properties of the MPPM are studied by the impedance tube experiment. Results show that the membranes have a significant influence on the sound impedance. The sound absorption performance of MPPM gradually increases with the increase of the membrane area. The single-layer MPP with some small area membrane cells may have the same effect and single large area membranes. By adjusting the size of the membrane cells, one can implement a sound absorber with a wider absorption bandwidth and higher absorption peaks than the single-layer MPP.     

Sound field prediction in long enclosures with branches: A combined method

The propagation of sound in long enclosures with branches has been studied theoretically and experimentally, and an efficient combined method is proposed to predict the sound field in long enclosures with branches. Based on the wave-acoustics theory, the theoretical analysis of the sound field of the long enclosures with branches is performed. This paper also investigated the sound field prediction of long enclosures with branches, by using the acoustic modeling program, ODEON. The results obtained by the theoretical analysis and the numerical simulation ODEON are compared with the experimental measurements, and the characteristics of the two methods for predicting the sound field of long enclosures with branches are analyzed. Compared with the experimental results, it is found that: (1) the results predicted by the theoretical analysis fluctuate relatively large with respect to the source-receiver distance, and the sound pressure level (SPL) attenuation obtained is smaller than that measured; and (2) the results predicted by the numerical simulation is smoother, and the calculated SPL attenuation is larger than that measured. To effectively predict the sound field of long enclosures with branches, a combined numerical method is thus proposed. The effectiveness of the proposed combined method is demonstrated by the scale-model experiments.     

Inverse acoustical characterization of natural jute sound absorbing material by the particle swarm optimization method

For modeling of jute as acoustic material, knowledge of its non-acoustical parameters like porosity, tortuosity, air flow resistivity, thermal and viscous characteristic lengths is a prime requisite. Measurement of these non-acoustical parameters is not straightforward and involves a dedicated measurement setup. So in order to overcome this issue, the inverse acoustical characterization can be used. In this paper, the particle swarm optimization method (PSO) is used as an optimization method. This method estimates the non-acoustical parameters of jute material in felt form by minimizing the error between experimental and theoretical sound absorption data. In this work, the impedance prediction models for fibrous materials like Johnson–Champoux–Allard model with rigid and limp frame and Garai–Pompoli model is used for sound absorption coefficient calculation by the transfer matrix method along with the PSO. The inverse estimated non-acoustical parameters for jute material are then compared with estimated and experimentally measured parameters for jute felts. Using these inversely predicted parameters, sound absorption of multilayer sound absorbers is also studied.     

基于声场重建的材料吸声系数测量方法

针对现有方法对材料吸声系数进行现场测量时存在低频测量误差大的问题,本文提出了一种利用扬声器线阵列对材料吸声系数进行现场测量的新方法。该方法使用基于能量比值约束的最小二乘法在待测材料表面进行平面波声场重建并结合双传声器传递函数法对材料的吸声系数进行测量。数值仿真表明在100～1600 Hz频率范围内,新方法在未加约束时能够对材料的吸声系数进行准确测量。在半消声室中利用新方法测量了三聚氰胺泡沫的吸声系数,分析了能量比值约束值对测量结果的影响,并和阻抗管以及其它两种现场测量方法的测量结果进行了对比。结果表明该方法能够对吸声材料在160～1600 Hz频段内的吸声系数进行准确测量,并且相较于现存的现场测量方法,新方法具有更低的测量频率下限。