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.     

Reception plate method for characterisation of structure-borne sound sources in buildings: Assumptions and application

A method for characterisation of structure-borne sound sources is proposed and investigated for the special but common case of machines in heavy-weight homogeneous building structures. The method is based on the concept of the reception plate where the total structure-borne sound power from the machine under test is assumed equal to the power dissipated by a plate attached to the machine. The method is relatively simple and allows comparison of sources on a power basis, and of tests results at different laboratories. Additionally the data obtained is in a form suitable for transformation into an installed structure-borne power and thence for the resultant sound pressure generated in buildings. The method is validated by cross-spectral and mobility methods. A study of the uncertainty of the power estimate was performed by numerical modelling and measurement.     

Correspondence between two types of rating indices for the heavy weight floor impact sound insulation of residential buildings

Of the two types of rating indices for the heavy weight floor impact sound insulation, the method of utilizing a rubber ball impact source combined with A-weighted sound level and the method utilizing a tire impact source combined with L-rating curve, the advantage of the former has been reported. In order to extend the advantage, the possibility was studied of estimating the rating utilizing the rubber ball impact source, based on the measurement results utilizing the tire impact source, especially for the case of a double leaf wooden floor. The correlation between the indices is not high enough to estimate one of them directly from the other with an accuracy not incorrectly estimating the rating grade of 5 dB step. The use of predictor variables, such as the special specifications of the double leaf wooden floor, for example, the use of sound insulation sheet, and the floor impact sound levels in the 31.5-Hz, 63-Hz and 125-Hz bands, is possibly able to increase the accuracy. Three principal types of multiple regression equation were derived through the analysis of measurement results in existing residential buildings.     

Justification of standardized level differences in rating of airborne sound insulation between dwellings

It has long been recognized that single-number quantities R′_w, D_nT,w or D_n,w result in different conclusions in objective rating of airborne sound insulation between dwellings. The difference between the values of these single-number quantities (SNQ), however, does not prove which of them describes the sound transmission between rooms most correctly. The main object of this article was to study which SNQ correspond best with transmitted living sound levels in buildings when reverberation time, volume of receiving room and sound insulation are taken into account. Data of 100 field measurements of airborne sound insulation were collected as well as 207 reverberation times of furnished rooms. The transmitted sound levels of living sounds were evaluated on the basis of known living sound spectra and measured level differences D. The results show that the SNQs standardized to reference reverberation time of 0.5 s lead in all cases to best correlation between the SNQs and the sound levels of transmitted living sounds. It was also checked whether the rating by D_nT,w would lead to higher transmitted sound levels of living sounds in larger rooms, but this was not detected. The use of D_nT,w makes rooms of different volumes equal in regard to required sound insulation between them. It is thus justified to replace R′_w with D_nT,w as the SNQ for rating the airborne sound insulation. Widening the frequency range down to 50 Hz or up to 5000 Hz did not give noteworthy improvement in the correlation.     

基于平面声源进行结构声辐射有源控制的实验研究

采用分布式平面声源作为次级声源,对振动钢板的声辐射进行了抵消实验,验证了以往研究中的一系列关键理论。实验研究结果表明:一个平面声源可以控制钢板奇-奇模态的声辐射,两个平面源可以控制结构偶-奇或奇-偶模态的声辐射,同时也可以控制结构奇-奇模态的声辐射;平面声源的面积和布放位置对降噪效果有重要影响,采用单个平面声源控制时,平面声源面积越大,控制效果越好;基于近场声压的误差传感策略是有效可行的,实际中,将近场测量面的声功率作为有源控制的目标函数与总声功率作为目标函数是一致的;控制后远场声压和声强都得到有效降低,部分区域的声能向声源流动,近场声压及声强分布也发生显著变化。     

Study of the uncertainty of façade sound insulation measurements: Analysis of the ISO 12999-1 uncertainty proposal

The result of a measurement is an approximation of the true value of the measurand and is complete when it is accompanied by its uncertainty. Building acoustics requires an assessment of the uncertainties that is understandable and corresponds closely to reality. The new standard ISO 12999-1 gives general uncertainty values for typical sound insulation measurements. The objective of this work is to determine the most accurate method for evaluating the uncertainty of in situ façade sound insulation measurements for both the D_ls,2m,nT values in one-third octave bands and the global magnitude D_ls,2m,nT,w. We establish a comparative analysis between the uncertainty values proposed by the standard ISO 12999-1, the uncertainty values deduced from interlaboratory activities and the average uncertainties deduced from individual calculations for each in situ measurement. The comparison is based on uncertainty calculations for around 1000 in situ façade sound insulation measurements made by our laboratory. The uncertainties given by the standard ISO 12999-1 for D_ls,2m,nT in one-third octave bands are, at low and high frequencies, higher than the values deduced from individual calculations and smaller than the calculated values at mid frequencies. We believe that for D_ls,2m,nT, it is advisable wherever possible to make individual uncertainty calculations for each in situ façade measurement. Nevertheless, the comparison with ISO 12999-1 points to the suitability of including some uncertainty components in the calculation, such as the related to the measurement procedure or source directivity, which are not normally considered in the uncertainty evaluation. Although we have clearly endorsed the use of individual calculations to determine the uncertainty of the sound insulation magnitude in one-third octave bands, we believe the uncertainty proposed by standard ISO 12999-1 could be a more realistic and reasonable approximation for the global magnitude D_ls,2m,nT,w. Therefore if an individual calculation of the uncertainty of the global magnitude is required the Monte Carlo simulation has been shown to be a good method.     

单层传声器阵列重建相干声场的近场声全息方法研究

针对传声器阵列两侧存在相干声源的非自由声场重建问题,提出基于球面谐波函数扩展近场声全息理论的相干声场重建方法。该方法在已知测量面两侧声源几何位置时,使用单层传声器阵列获取测量面处的声压分布,通过最小二乘法获得与目标声源和干扰噪声源响应对应的最优球波函数扩展项数和最优系数向量,结合测点位置的空间坐标进行声波分解,并分别重建出各声源在测量面上的声压分布。为了验证方法的有效性,分别给出了相干噪声源为球形声源和非球形声源的仿真验证,并在全消声室内对双扬声器产生的相干声场的重建进行了实验验证。结果表明:该方法对球形声源和非球形声源干扰下的声场重建都具有较好的效果,球形声源干扰下的重建精度更高。     

Assessment of a simplified experimental procedure to evaluate impact sound reduction of floor coverings

The impact noise reduction provided by floor coverings is usually obtained in laboratory, using the methodology described in the standard EN ISO 140-8, which requires the use of standard acoustic chambers. The construction of such chambers, following the requirements described in the EN ISO 140-1, implies a significant investment, and therefore only a limited number exists in each country. Alternatives to these standard methodologies, that allow a sufficiently accurate evaluation and require lower resources, have been interesting many researchers and manufacturers. In this paper, one such strategy is discussed, where a reduced sized slab is used to determine the noise reduction provided by floor coverings, following the procedure described in the ISO/CD 16251-1 technical document. Several resilient coverings, floating floors and floating slabs are tested and the results are compared with those obtained using the procedures described in the standards EN ISO 140-8 and EN ISO 717-2.     

Measurement of airborne sound insulation of timber noise barriers: Comparison of in situ method CEN/TS 1793-5 with laboratory method EN 1793-2

Recent progress in the development of European standards has allowed the in situ testing of roadside noise barriers. CEN/TS 1793-5 describes a test method using maximum length sequences (MLS) for the characterisation of airborne sound insulation. However, many barriers are tested according to a laboratory standard, EN 1793-2, based on measurements carried out in reverberant chambers and in the case of timber barriers with a relatively low airborne sound insulation it is not clear to what extent the results of the two tests compare. The paper describes the results of tests carried out using both methods. Six samples of timber barrier were compared including single-leaf and double-leaf constructions and single-leaf constructions with an absorptive core. Very good agreement was found especially when account was taken of the valid frequency range in each test method. The results open up the possibility of routinely evaluating the performance of timber barriers at the roadside where build quality can be variable and there are concerns that the acoustic performance may not match that obtained under laboratory test conditions where typically the barrier is more carefully constructed.     

Development of multiple drywall with high sound insulation performance

Experimental studies for the development of multiple drywalls with a high sound insulation performance are performed. Firstly, a means of preventing the sound insulation deterioration due to the coincidence effect at high frequencies is investigated by layering two plasterboards with different physical characteristics. Based on the results, a double drywall with a sound insulation performance of R_w = 61 is developed. Further more, a double drywall of R_w = 64 , a triple drywall of R_w = 86 and a quadruple drywall of R_w = 90 are developed.     

The performance of resilient layers made from recycled rubber fluff for impact noise reduction

This paper reports an investigation of a new kind of material and its acoustical performance. The potential of recycled materials made from rubber fluff for reducing impact noise was assessed according to EN ISO 140-8:1997. The performance of these materials was compared to those of some commercially available underlays.     

Impact sound insulation and viscoelastic properties of underlay manufactured from recycled carpet waste

This paper reports an investigation of the impact sound insulation performance of a range of materials made from recycled carpet tiles and provides a comparison with the performance of some commercially available acoustic underlays. The impact testing is carried out using a specially designed rig. It is demonstrated that good quality acoustic materials can be successfully manufactured from a granulated mix of industrial carpet waste. The effects of the grain to fibre (G:F) mass ratio, binder concentration and particle size distribution on the acoustic performance is investigated. It is shown that the optimum G:F ratio should be close to the mass ratio of the backing material to the pile material in many types of commercial carpet tiles (60:40). Sieving the granular waste and producing samples containing a single class of particle size does not enhance the impact sound insulation performance. These are important findings, which should ensure an efficient, cost-effective, full-scale manufacturing process. A formulation has been developed which yields samples with optimum impact sound insulation capability. This optimised sample compares favourably with the commercial underlays tested on the impact rig. The dynamic mechanical properties of the developed underlays have also been investigated to provide a better understanding of their influence on the impact sound insulation.     

Anomalous sound propagation due to the horizontal variation of seabed acoustic properties

Sound speed profile and the bottom acoustic property are two of the most important factors, which influence the sound propagation in shallow water. The activities of the internal waves make the temperature of the sea-water varying with the time and space, and then affect the sound propagation in the sea. In 1991 Zhou and his colleagues postu-lated that unusually high transmission losses (TL) over a limited frequency range found in annual measurements taken in the Yellow Sea was due to the in…     

经典局域共振型水声超材料的吸隔声性能研究*

基于水声超材料吸声机理和多层平行介质平面波理论,建立局域共振型水声超材料结构,通过COMSOL进行建模计算,研究该结构的吸声性能机理,此外为了验证钢背衬的隔声性能,在该水声超材料结构基础上添加一层0.005m厚的钢背衬进行仿真对比。研究结果表明,在频段为200Hz-4000Hz时,水声超材料声学性能较好,吸声性能整体较优,且添加钢背衬的水声超材料隔声性能较优,甚至在某频率点达到15dB的隔声差值;此外通过位移场图进一步揭示水声超材料的吸声机理,发现水声超材料结构的位移场和钢背衬都对吸声性能会产生影响,钢背衬通过影响共振吸收来影响吸声性能,而位移场则通过位移幅度大小影响吸声性能。     

基于声吸收谱峰值点的天然气燃烧特性检测理论

天然气的成分构成会随产地来源变化而不同, 使其具有不同的燃烧特性和经济价值.本文利用声吸收谱峰值点随气体成分变化而改变的声分子弛豫现象, 提出一种天然气燃烧特性检测理论.它基于两频点上声测量值可合成声吸收谱峰值点, 且依赖于频率的声吸收谱可由峰值点重建的物理原理; 可利用峰值点对应的特征量——弛豫频率和弛豫吸收最大值与气体成分的关系, 从两个维度同时定量检测天然气成分.该理论避免了传统上测量声吸收谱峰值点方法需要不断改变气体腔体压强的问题, 还具有无需测量气体密度的优点.     

基于定量分析的气固两相流声速模型综述

声波法是多相流测量的一种有效方法,可靠的声速模型是其中时差法等测量的理论基础。该文系统总结了国内外不同学者所建立的气固两相声速模型。为直观地呈现其差异、发展与局限,该文以颗粒相浓度的影响为例,采用模拟计算和实验测量相结合的方法对其中不同典型声速模型进行了定量分析与比较。结果表明,传统的拟均相介质模型声速随颗粒浓度变化,与在其基础上考虑声波特性的改进模型,以及分别基于相间耦合和颗粒散射的声速模型差异均较大,且显著偏离实验测量值。其主要源于传统的拟均相介质模型未考虑两相间相对运动的影响;而考虑相间相互作用的声速模型间虽有不同差异,但均与实验测量值较为接近,根据稀相区实验研究,所得声速值均较实验值偏小。     

基于等效参数反演的敷设声学覆盖层的水下圆柱壳体声散射研究

应用了一种等效方法计算敷设声学覆盖层无限长圆柱壳体水下声散射特性.等效方法的核心是忽略复杂声学覆盖层内部的声学结构,将其作为具有等效材料参数的均匀阻尼层进行建模,该均匀阻尼层具有和原覆盖层相同的复反射系数.进而,应用COMSOL Multiphysics软件建立敷设均匀阻尼层圆柱壳体的有限元模型并求解其声散射特性.等效方法的关键是等效材料参数的获取.采用充水阻抗管实验和有限元数值实验两种方法获取声学覆盖层贴敷在与壳体具有相同厚度、相同材料背衬条件下的复反射系数,在此基础上,基于遗传算法反演材料的等效参数.研究表明,等效参数具有频变特性,且尽管等效杨氏模量和等效泊松比在频率范围内存在较大波动,但是等效前后复反射系数仍保持一致.为了验证等效方法求解壳体声散射特性的准确性,同时建立了敷设声学覆盖层壳体的完整有限元模型,将覆盖层内部声学结构进行精细建模,并求其声散射特性.结果表明,两种方法求得的形态函数符合得较好,在整个频率范围内平均误差大约为1 d B.     

基于最差性能优化的运动声源稳健聚焦定位识别方法研究

基于被动合成孔径原理,提出了一种具有高稳健性的运动声源高分辨聚焦定位识别方法.该方法采用综合优化手段,通过矢量最大似然聚焦定位算法生成虚拟阵列坐标及数据矩阵,进而利用基于最差性能优化的稀疏虚拟阵列聚焦算法,获取稳健的高分辨定位识别效果.理论及仿真研究表明,该方法对于非匀速运动以及与基阵存在运动倾角的复杂情况具有较强的适用性,聚焦空间谱表现出更大的动态范围、更为尖锐的聚焦峰尺度以及更强的背景噪声起伏压制能力.湖上试验进一步验证,在高分辨最小方差信号无畸变响应法(MVDR)聚焦算法动态范围仅为3.5 dB的相 关键词： 稳健性 运动噪声源定位识别 矢量阵 最差性能优化