非对称夹芯板隔声量的解析计算模型及影响因素

提出了一种计算上下面板非对称的三明治夹芯板隔声性能的方法。通过对非对称夹芯梁表观抗弯曲刚度的计算,得到对应夹芯板随频率变化的表观抗弯刚度,代入4阶的控制方程,应用模态展开法可以方便地计算简支非对称夹芯板的隔声量。对4种定制的3层非对称碳纤维夹芯板进行了理论计算和实验测试对比,在频率范围100～3150 Hz内,计权隔声量误差在3 dB以内。着重分析了面板对称性、芯层剪切模量对隔声性能的影响,发现在夹芯板面密度一定时,芯层剪切模量对夹芯板的隔声性能影响最为显著。当芯层剪切模量较小时,上下面板非对称分布导致吻合频率显著降低,对夹芯板的整体隔声亦不利。     

复材结构刚度与隔声量的计算及参数优化

论文旨在满足结构刚度指标的前提下最大程度地提高复合材料(以下简称"复材")结构的隔声性能。首先针对复材结构进行刚度分析,在铺层数和铺层比例不变的前提下,分析不同铺层构型对结构刚度的影响。然后利用统计能量分析法,确定铺层角度对结构隔声性能的影响,并与试验结果进行对比验证模型的有效性。最后以铺设在复材壁板上的隔音棉厚度和密度为两个优化参数,分析不同厚度和密度的隔音棉的插入损失,并进行参数最优化分析,寻找最佳组合方式。得出结论:不同铺设角度顺序对复材整体结构的弯曲刚度和吻合效应频率有影响,在相同尺寸和边界条件下,构型1屈曲稳定性承载能力较强,隔声效果最好,铺层方式最优;隔音棉密度对插入损失影响较小,而隔音棉厚度对插入损失影响较大。论文选取的隔音棉密度和厚度已经使壁板、隔音棉及内饰板的组合结构隔声量达到了收敛状态,是最优化的组合设计。     

复合材料机身结构声学特性及影响参数分析

针对复合材料(以下简称"复材")结构进行声振分析,通过无限大障板理论和波动方程,分析复材平板和曲板结构的传声损失,并利用统计能量法分析壁板的隔声性能,与文献中的实验结果进行对比,验证建模的有效性。然后将复合材料机身结构等效成一个复材圆柱壳体结构,分析不同参数,包括压差、曲率半径、长度、铺层角度、纤维材料、加筋等对结构隔声性能的影响。最后与金属机身结构进行隔声性能对比,发现:在环频率与吻合效应频率之间,金属机身结构的传声损失明显大于复材机身结构,而在吻合效应频率以上频段,由于复材结构的吻合效应频率向低频移动,其传声损失好于金属机身结构。     

声辐射阻测量系统设计及测量精度影响因素分析*

在噪声控制领域,声辐射阻是一个重要的声学变量,在产品的设计阶段,可以通过改变结构表面形状来改变结构的声辐射阻抗,从而达到降噪的目的。本文基于集中参数模型,设计了测量设备,搭建了实验测量系统,并通过对无限大障板上圆形活塞声源的声辐射阻的测量对影响实验测量结果的因素进行了研究,之后对消音器入口处辐射阻进行了测量。测量结果表明:该实验测量系统具有操作简单,测量方便快捷,测量结果精度高等特点,可用于确定结构表面声辐射阻矩阵。     

弱耦合封闭声腔的声辐射模态理论与计算

有源结构声控制是耦合封闭声腔的声辐射控制的有效方法。在此前的研究中有学者提出了\     

复杂结构声辐射模态的计算

结构辐射阻矩阵的特征向量就是其声辐射模态,复杂结构的辐射阻矩阵获取困难阻碍了声辐射模态理论的进一步应用。为此提出一种基于等效源方法的复杂结构辐射阻矩阵计算方法,由此形成了一套完整的计算复杂结构声辐射模态方法。最后通过仿真算例对影响结构辐射阻矩阵计算精度的因素进行了分析,给出了复杂结构辐射阻矩阵构造的一般原则。理论推导和数值仿真算例表明所提出的复杂结构声辐射模态计算方法是有效的。该方法简化了复杂结构声辐射模态的计算,计算效率较高。     

混凝土箱梁相似模型结构噪声对比分析*

为探讨混凝土箱梁噪声的时变特性,以京沪高铁32 m混凝土简支箱梁为原型,制作了1:10的缩尺模型,通过模态试验的方法验证箱梁模型与原型的相似关系,通过声学试验验证箱梁声学计算模型的正确性。然后,建立了箱梁缩尺模型与原型两种计算模型,利用有限元和边界元法求出两种模型的瞬态结构噪声。研究发现,箱梁缩尺模型与箱梁原型的材料参数满足一定关系,模型试验的方法能够验证箱梁模型与箱梁原型之间符合相似关系,箱梁模型的振动噪声测试结果能真实反映原型振动噪声水平。两种模型的结构噪声在时域内声压级及对应场点的声压存在一定相似关系。该研究可为箱梁缩尺模型结构噪声反演至箱梁原型提供依据,所采用的方法和得到的结果对桥梁结构振动与声辐射实验研究具有参考作用。     

气凝胶纳米多孔隔热材料传热计算模型的研究

本文研究并建立了气凝胶复合隔热材料传热计算模型.针对气凝胶纳米多孔材料的分形结构特征,结合规则交叉球杆结构,提出了气凝胶纳米多孔材料的分形交叉球杆结构模型,并以此结构模型为基础,建立了气凝胶纳米多孔材料热导率分形计算模型,模型中同时考虑了尺寸效应对气相、固相传热方式的影响.对气凝胶中添加的遮光剂、增强纤维等微米典型结构,以Mie辐射散射理论为基础,结合Rossland扩散近似模型,考虑了辐射传热对热量传递的增强作用;同时结合经典的两相系统等效热导率计算公式,获得复合材料的辐射导热耦合热导率计算模型.本文从纳米尺度的气凝胶多孔材料传热模型到微米尺度的气凝胶复合隔热材料传热模型,建立了完整的气凝胶纳米多孔复合隔热材料等效热导率计算模型.模型与多个文献中气凝胶材料热导率实验数值进行比较,获得了满意的结果,验证了模型应用于气凝胶复合隔热材料等效热导率预测计算方面的有效性.     

新型列车侧墙内装板声学分析、优化及应用*

为了开发与应用新型列车车体降噪内装结构,基于混合FE-SEA法对轨道车辆用新型橡胶泡棉夹芯板进行隔声与声辐射预测建模,并进行了试验验证,进而利用该模型分析了橡胶泡棉孔隙率与芯皮厚度比对其隔声性能、声辐射性能的影响规律,并通过敷设阻尼层优化了其声学性能。最后,在侧墙组合结构的声学设计中评价了其实际应用效果。结果表明：随着孔隙率的逐步下降,橡胶泡棉夹芯板隔声量上升趋势较为明显,而辐射声功率持续降低;随着芯皮厚度比的逐步提高,夹芯板隔声量呈略微上升趋势,辐射声功率则相应降低。在远离声源一侧的橡胶泡棉蒙皮外侧敷设阻尼层的效果最优,优化后夹芯板计权隔声量提高0.7dB,总声功率级降低0.7dB;相较于传统木质胶合板和铝蜂窝板,橡胶泡棉夹芯板相较于传统内装板材在结构隔声设计中具有轻量化优势。     

Approximate method for obtaining source quantities for calculation of structure-borne sound transmission into lightweight buildings

An approximate approach is described, for obtaining the source quantities required for the calculation of structure-borne sound power from machines into supporting lightweight building elements. The approach is in two stages, which are based on existing international Standards for measurement. The first stage involves direct measurement of the source free velocity at each contact, to give the sum of the square velocities. The second stage is based on the reception plate method and yields the single equivalent blocked force, which approximates the sum of the square blocked forces. The applicability of the source data obtained has been investigated in a case study of a fan unit on a timber joist floor. The approach contains several significant simplifying assumptions and the uncertainties associated with them are considered. For the case considered, the power transmitted into the floor is estimated by the approximate method to within 5 dB of the true value, on average.     

Assessment of sandwich models for the prediction of sound transmission loss in unidirectional sandwich panels

The consistent higher-order approach and the two-parameter foundation formulation are used for the derivation of sound transmission loss in symmetric unidirectional (infinitely wide) sandwich panels with isotropic face sheets. In both models, transmission loss is calculated using decoupled equations representing symmetric and anti-symmetric motions of a sandwich panel. The closed-form expressions for impedances and transmission coefficient of a symmetric sandwich panel with an isotropic core are derived for the two-parameter foundation model. A comparison between the numerical predictions based on the two sandwich models and available experimental data shows that the consistent higher-order formulation can be used to predict the transmission loss in symmetric sandwich panels with both honeycomb and isotropic cores. For prediction of transmission loss of symmetric sandwich panels with an isotropic core, the two-parameter foundation model is more convenient, while the consistent higher-order approach is more accurate.     

双层弹性支撑板的水下宽带隔声

为实现水下宽带隔声,提出了一种由弹性元件支撑两块刚性端板构成的双层弹性支撑板结构。采用弹簧振子振动分析法和声传播理论,建立了平面波入射的水下隔声理论模型,分析了结构参数对隔声量的影响规律,结果表明足够小的弹性元件单位面积弹性系数或足够大的端板单位面积质量都可以连续一致地提高隔声量.仿真分析了双层弹性支撑板的振动位移和声输入阻抗,比较了双层弹性支撑板与连续介质层的隔声特性,结果表明,降低弹性元件质量,有助于在低频段消除半波全透射现象.在同厚度、同质量、同静态压缩率条件下,双层弹性支撑板能更好的降低两侧流体的振动及声耦合,隔声频带更宽,带内一致性更好,隔声量更大.     

Reception plate method for characterisation of structure-borne sound sources in buildings: Installed power and sound pressure from laboratory data

In a companion paper, a laboratory method is described to obtain the structure-borne sound power of machines before they are installed in heavy-weight buildings. The laboratory method is based on the concept of the reception plate. In this paper, the method is shown to provide appropriate input data for the prediction of the installed structure-borne power, and thence the resultant sound pressure level in rooms removed from the room containing the machine. Case studies of two common sources are described: a whirlpool bath and a water cistern. It is shown that the method can be incorporated into recently proposed standard prediction models and that sound pressure levels in buildings can be predicted.     

Using transient and steady-state SEA to assess potential errors in the measurement of structure-borne sound power input from machinery on coupled reception plates

Isolated reception plates provide an engineering approach to quantify the structure-borne sound power input from machinery through the measurement of the spatial-average velocity level and structural reverberation times. For applications in building acoustics there are practical and economic reasons to consider using coupled reception plates formed by solid heavyweight walls or floors that are structurally coupled to other building elements. This paper uses transient and steady-state statistical energy analysis to investigate how the errors depend upon the building structure to which the coupled reception plate is connected. It is shown that the problem is twofold. Firstly, in the low- and mid-frequency ranges, the steady-state velocity level on the coupled reception plate is increased by energy returning from other coupled plates. Secondly, the structural decays on the coupled reception plate have significant curvature due to returning energy; hence short evaluation ranges are needed to minimise the error when determining the total loss factor. This leads to a problematic situation where the coupled reception plate appears to give the correct answer due to the error in the energy cancelling out the error in the total loss factor. The latter error can be minimised using short evaluation ranges for the structural reverberation time.     

Optimal design of acoustical sandwich panels with a genetic algorithm

An optimization study is performed to design a sandwich panel with a balance of acoustical and mechanical properties at minimal weight. An acoustical model based on higher-order sandwich beam theory is used with mechanical analysis of the maximum deflection at the center of the sandwich panel under a concentrated force. First, a parametric study is performed to determine the effects of individual design variables on the sound transmission loss of the sandwich panel. Next, by constraining the acoustical and mechanical behavior of the sandwich panel, the area mass density of the sandwich panel is minimized using a genetic algorithm. The sandwich panels are constructed from eight face-sheet and sixteen core materials, with varying thicknesses of the face sheets and the core. The resulting design is a light-weight, mechanically efficient sound insulator with strength and stiffness comparable to sandwich structures commonly used in structural applications.     

墙体设置接线盒隔声性能影响的实验室研究

在轻质墙体(轻钢龙骨类板墙)及重质墙体(240 mm砖墙)上设置不同数量的接线盒前后,对墙体的空气声隔声性能的影响进行了实验室试验。并对试验结论进行了分析,得出了不同类型墙体设置接线盒后,对墙体空气声隔声性能的影响因素及处理方法。     

Subjective evaluations of sound radiated by impacted plates, using the design of experiments method

This study combines physical and subjective approaches to evaluate the sound quality of impacted plates. A numerical model, based on the Hertz law of contact, has been used to determine the sound pressure level at any point in space resulting from an impact. Sounds synthesized using this model and those from experiments can then be exploited in a physical analysis and/or a subjective analysis of the effects associated with variations in parameters. Here the influence of certain physical parameters on the sound perception of impacted plates is evaluated through a design of experiments method and a subjective test of preference. The subjective test is based on an estimate of preference between two pairs of synthetic sounds by varying several structural parameters at the same time. This differs from other studies that vary only one parameter at a time and fix the other parameters.