在气液混相介质中测量声透射损失

用频率分别为0．5,1,1．25,2,2．5MHz的超声波,对气水混相介质声透射损失进行了测量,结果发现：声透射损失随含气量的增加急剧增大．在气泡大小、分布一定的情况下,可以用声透射损失来反映混相介质中的含气量．     

Influence of specimen frame on sound transmission loss measurement

Increased sound transmission through several wall specimens as a result of interaction with the specimen mounting frame is described. The effect of the frame is reduced by shielding it from the sound fields.     

半波长管传声损失分析

1/4波长管和Herschel-Quincke(HQ)管具有良好消声潜力,在其固有频率附近具有很高的消声量级,为了将这种消声潜力在更小的安装空间内和更宽的频带上发挥出来,设计了一种新的半波长管,通过对多管传声损失理论模型的推导,运用数值计算的方法,分析了传声损失的影响因素并对多分支管模型进行宽频带尺寸设计,最终实现在3...     

Exploiting the laboratory measurement of sound transmission loss by the sound intensity technique

The sound intensity measurement technique is employed to determine the transmission loss of panels in a laboratory situation. An experimental procedure is established, the technique validated, and subsequently exploited to determine transmitted intensity contours for two sizes of panel, as well as to examine the influence of a deliberately introduced construction fault.     

Experimental analysis on air-to-water sound transmission loss in shallow water

The research of propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial targets from underwater.In order to study the propagation characteristics of air-to-water sound transmission in shallow water,State Key Laboratory of Acoustics,Institute of Acoustics,conducted an experiment in the South China Sea in March,2013.During the experiment,multi-frequency signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone,and the distance between the hooter and the hydrophone was from 2.4 km to 9.8 km approximately.Through analyzing experimental data in this work,the experimental air-to-water transmission loss at frequencies128 Hz and 256 Hz is estimated up to 9.8 km in range,and its oscillation structure is evident.The wave-number integration approach is used to simulate theoretical air-to-water transmission losses,which are in good agreement with experimental values and to explain the experimental air-to-water sound transmission characteristics.     

空气中声源激发浅海水下声场传播特性的实验研究

为了获得空气中远距离声源激发水下声场的精细结构,2013年3月,声场声信息国家重点实验室在南海海域进行了一次空气中声源激发水下声场的实验。采用汽笛作为空气声源,海底放置水听器作为接收,在实验过程中,发射船由距离水听器2.4 km处行驶至9.8 km。本文对该次实验数据进行分析,获得了收发距离远达9.8 km、频率分别为128 Hz和256 Hz的声传播损失曲线,该曲线随传播距离变化存在清晰的震荡结构.利用波数积分方法计算实验环境下的水下声场理论值,并对获得的声场传播特性进行了较好的物理解释。     

The influence of sills and reveals on sound transmission loss

A review is made of existing works concerning the effects of sills and reveals on the transmission of sounds through windows and panels. New data is presented which supplements our knowledge base and a sill and reveal design guide is proposed for the purpose of increasing the sound transmission loss of windows or light panels.     

测量白油中声透射损失的教学实验装置

通过实验发展：在测量范围内，声透射损失随含气量线性增大。在气泡大小、分布一定的情况下，可以由声透射损失来测量油中的含气量。     

Prediction of outdoor sound transmission loss with an artificial neural network

An artificial neural network is developed for rapid prediction of sound transmission loss (TL) during propagation outdoors. The network predicts TL for a nonturbulent atmosphere from inputs involving the source/receiver propagation geometry (height range: 0-5 m, horizontal separation distance: 100-900 m), source frequency (range: 20-200 Hz), ground properties, and atmospheric refractive profile characteristics. A parabolic equation (PE) code generates the training and test data sets for the network. To ensure that a minimal set of input parameters is used in the network training, a nondimensional version of the PE and accompanying boundary, initial, and atmospheric conditions is developed. A total of 10 independent, nondimensional input parameters are found to be necessary for the training. Approximately 27,000 random cases involving these 10 parameters are generated used to train networks with varying numbers of neurons. The root mean square (RMS) error between random test cases solved by the PE and corresponding neural network predictions was 2.42 dB when a sufficient number of neurons (about 44) are included in the hidden layer. Also, only 18% of the cases resulted in RMS errors that were greater than 2 dB.     

Simple sound transmission loss measurements using a modified impedance tube technique

A method of comparing the sound transmission characteristics of various materials, and combinations of materials, is presented, using a modified impedance tube technique. The procedure proved to be relatively quick and inexpensive in comparison with standard reverberation suite tests, and is therefore particularly useful for the qualitative ranking of multiple samples.The limitations of the technique are discussed in some detail, and particular emphasis is given to the problems of small sample size and method of mounting in the apparatus.     

Vibro-acoustic response and sound transmission loss analysis of functionally graded plates

This paper presents analytical studies on the vibro-acoustic and sound transmission loss characteristics of functionally graded material (FGM) plates using a simple first-order shear deformation theory. The material properties of the plate are assumed to vary according to power law distribution of the constituent materials in terms of volume fraction. The sound radiation due to sinusoidally varying point load, uniformly distributed load and obliquely incident sound wave is computed by solving the Rayleigh integral with a primitive numerical scheme. Displacement, velocity, acceleration, radiated sound power level, radiated sound pressure level and radiation efficiency of FGM plate for varying power law index are examined. The sound transmission loss of the FGM plate for several incidence angles and varying power law index is studied in detail. It has been found that, for the plate being considered, the sound power level increases monotonically with increase in power law index at lower frequency range (0–500 Hz) and a non-monotonic trend is appeared towards higher frequencies for both point and distributed force excitations. Increased vibration and acoustic response is observed for ceramic-rich FGM plate at higher frequency band; whereas a similar trend is seen for metal-rich FGM plate at lower frequency band. The dBA values are found to be decreasing with increase in power law index. The radiation efficiency of ceramic-rich FGM plate is noticed to be higher than that of metal and metal-rich FGM plates. The transmission loss below the first resonance frequency is high for ceramic-rich FGM plate and low for metal-rich FGM plate and further depends on the specific material property. The study has found that increased transmission loss can be achieved at higher frequencies with metal-rich FGM plates.     

An experimental investigation on the directional distribution of incident energy for the prediction of sound transmission loss

It is suggested from a previous theoretical study that an angular distribution function can be successfully used for describing the directional distribution of incident energy on the wall, instead of the field incidence assumption being used in the prediction of sound transmission loss. This study is devoted to an experimental investigation on the directionality of incidence sound field for validating the underlying assumption in the theoretical work. To this end, the directional magnitudes of incident energy on a wall in a reverberation chamber are measured by employing the sound intensimetry. The experimental results suggest that the transmission coefficient formula should be revised by introducing a proper angular distribution function as a weighting function for describing the directional energy density distribution, which replaces the conventional field incidence method. The revised formula is applied to the prediction of transmission loss for a double-leaf panel with an air cavity, in which its effectiveness is strongly supported by good agreements between measured and predicted values.     

Development of an optimised, standard-compliant procedure to calculate sound transmission loss: design of transmission rooms

A numerical procedure to estimate the transmission loss of sound insulating structures is proposed based upon the technology of acoustic measurements and standards. A virtual laboratory (VL), namely, a numerical representation of a real laboratory consisting of two reverberation rooms meeting certain sound field quality criteria is designed. VL is to be used for the numerical simulation of standardised measurements under predefined, controlled, acoustic conditions. In this paper, the design and optimisation of VL is investigated. The geometry of the transmission rooms is designed following first principles, in order for diffuse field conditions and sufficiently smooth primary mode distribution in the low frequency to be achieved. A finite element-based optimisation procedure, introduced by the author in previous work, is extended to arbitrarily shaped rooms. It is used to predict the appropriate local geometric modifications so as for improved mode distribution and smoother sound pressure fluctuations of the transmission rooms in the low-frequency range to be achieved and low-frequency measurement reproducibility and accuracy to be increased. Steady-state acoustic response analysis is performed in order to quantify the acoustic field quality of the virtual transmission rooms in the frequency range of measurements. A method to calculate the total absorption, A, of the receiving room is introduced by simulation of the reverberation time measurement procedure using Transient acoustic response analysis. The acoustic performance of VL is overall considered and is shown to meet in a sufficient degree, relative laboratory measurement standards in the frequency range of 100÷704 Hz.     

由脉冲波形与传播损失反演海底声速与衰减系数

根据黄海中部一次浅海声学实验获得的脉冲波形和传播损失数据进行海底声速和衰减系数的反演。本文在反演过程中:(1)考虑了海水深度的测量误差对反演结果的影响,并提出了一种消除该影响的方法。(2)反演得到的该海区海底衰减与频率呈非线性关系。(3)本文讨论了非均匀海底模型对海底反演结果的影响。     

用声透射损失测气一水混相介质中的含气量

本文利用超声检测中的穿透法,用频率为０．５ＭＨｚ、１ＭＨｚ、１．２５ＭＨｚ、２ＭＨｚ、２．５ＭＨｚ的声波,测量了气－水混相介质听声速比值和声透射损失,结果表明,在气泡大小,分布一定的情况下,可能用声透射损失来确定混相介质中的含量量,但不宜用声速比值。     

用声透射损失测气一水混相介质中的含气量

本文利用超声检测中的穿透法,用频率为０．５ ＭＨｚ、 １ＭＨｚ、 １．２５ＭＨｚ、 ２ＭＨｚ、 ２．５ＭＨｚ的声波,测量了气一水混相介质中的声速比值和声透射损失。结果表明：在气泡大小、分布一定的情况下,可能用声透射损失来确定混相介质中的含气量,但不宜用声速比值．     

Optimal poroelastic layer sequencing for sound transmission loss maximization by topology optimization method

Optimal layer sequencing of a multilayered acoustical foam is solved to maximize its sound transmission loss. A foam consisting of air and poroelastic layers can be optimized when a limited amount of a poroelastic material is allowed. By formulating the sound transmission loss maximization problem as a one-dimensional topology optimization problem, optimal layer sequencing and thickness were systematically found for several single and ranges of frequencies. For optimization, the transmission losses of air and poroelastic layers were calculated by the transfer matrix derived from Biot's theory. By interpolating five intrinsic parameters among several poroelastic material parameters, distinct air-poroelastic layer distributions were obtained; no filtering or postprocessing was necessary. The optimized foam layouts by the proposed method were shown to differ depending on the frequency bands of interest.     

空气中声源激发的浅海水下声场传播实验研究

为了了解空气中声源激发的水下声场传播特性,对此开展实验研究。2010年在南海北部海域进行了一次空气中声源激发水下声场实验,在水下成功地接收到远至4km处大功率扬声器在空中发射的脉冲声信号。本文通过分析实验数据,研究空气中声源激发的浅海水下声场传播特点。针对接收阵拾取的声传播信号信噪比低的特点,综合利用脉冲压缩以及波束形成方法提高接收信号的信噪比,得到收发距离1~4km、频率200~1000Hz范围内的传播损失实验值。在理论上,采用波数积分方法进行了声场数据模拟,结果表明理论计算的传播损失与实验结果较为一致。     

An improved method for determination of radiated sound power and sound transmission from large sources

The proposed method is an improvement of the methods for measurement of sound power level, in which the real sound source is represented by an equivalent monopole. It is based on a new concept, the equivalent acoustical centre, which is introduced and defined in the paper. The main assets of the method in comparison with the existing monopole-methods are a higher accuracy, a possibility of measuring at considerably shorter distances from the noise source, and a certain freedom in the choise of the measuring points around the source. Moreover, since the position of the equivalent monopole is obtained, it can be used for more accurate calculations of the sound transmission to the surroundings of the source. The method is particularly suitable for determination of sound power levels and sound transmission of noise radiated from large areas, such as industrial complexes, installations of petrochemical industries and the like. It can be especially useful in disputable cases of industrial plants that produce noise close to the legally permissible limit. The new method was first reported at the meeting of the Dutch Acoustical Society which took place in Utrecht on 22 November 1978.     

气泡幕的声透射损失和对水中壳体减振的实验研究

通过不同放气孔径和不同放气压差所形成的气泡幕的透声实验,获得了含气浓度在大范围内变化的气泡幕透声损失与频率关系的实验资料。在气泡幕对浮于水中壳体振动的影响的实验中,得到了气泡幕对壳体振动有明显抑制作用的实验结果。