Recommendations for the measurement of sound insulation between dwellings

National and international standards for the measurement of sound insulation allow the user considerable flexibility in his technique. Concerned that this could lead to systematic differences in results, seven leading test organisations in the UK formed a working group to devise a detailed procedure compatible with BS 2750 and ISO 140. The agreed procedure is explained and fully set out in this paper.A comparison between the results obtained by the groups using this agreed method and their individual methods is described. Some reduction in discrepancies was found with the new method but they were by no means eliminated.     

Calculation of airborne and impact sound insulation between dwellings

Some years ago a model was described for the calculation of the weighted airborne sound insulation between dwellings. Further work has been done since in order to increase the applicability of this model, including the extension to octave band calculations.Besides airborne sound, impact sound is also of importance. Therefore the calculation model has also been extended to impact sound insulation. These calculations are based largely on the same input data as for airborne sound. A new quantity however is the floor admittance. For homogeneous floors an existing model for the calculation of the admittance could be applied. For typical (Dutch) floor constructions consisting of concrete beams and plates a model for the admittance has been developed, based on admittance measurements in situ.Some examples are given of calculated and measured airborne and impact sound insulation.     

Case studies of attempts to improve the sound insulation between dwellings

The Building Research Establishment receives a steady stream of requests for information from people who are disturbed by noise from their neighbours and who wish to improve the sound insulation of their homes. Although the basic principles are well known, the problem is often complicated by the fact that both direct and flanking paths can make a significant contribution to the transmission of sound between dwellings. In the present state of knowledge each case needs to be treated individually and a full investigation is usually necessary before remedial treatment can be recommended. Methods for conducting the investigation are outlined in this paper and seven case studies are described in detail.     

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.     

Application of a finite-element model to low-frequency sound insulation in dwellings

The sound transmission between adjacent rooms has been modeled using a finite-element method. Predicted sound-level difference gave good agreement with experimental data using a full-scale and a quarter-scale model. Results show that the sound insulation characteristics of a party wall at low frequencies strongly depend on the modal characteristics of the sound field of both rooms and of the partition. The effect of three edge conditions of the separating wall on the sound-level difference at low frequencies was examined: simply supported, clamped, and a combination of clamped and simply supported. It is demonstrated that a clamped partition provides greater sound-level difference at low frequencies than a simply supported. It also is confirmed that the sound-pressure level difference is lower in equal room than in unequal room configurations.     

The sound insulation of wood joist floors in timber frame constructions

The results of an investigation of the sound insulation provided by wood joist floors between timber frame dwellings are described. The investigation was mainly concerned with impact transmission since available field data showed that the impact performance was, in general, worse than the airborne performance. The effects of changing various aspects of the floor design are discussed and limited guidance is given on the values of some floor parameters. Some tests have been carried out with the resilient layer bridged by nails and with the floor loaded. Suggestions are given for further research which is required to improve the understanding of sound transmission processes in wood joist floors.     

钢结构装配式住宅墙板连接方式对隔声性能的影响

为提升钢结构装配式住宅隔声性能,通过有限元法数值分析,比较了不同位置墙板的连接方式对房间隔声性能的影响.结果表明:侧墙墙板柔性连接处理对侧向传声的抑制作用显著,当侧墙墙板采用柔性连接后,房间的隔声量在低频段平均可以提升3 dB左右;公共隔墙墙板的柔性连接对房间低频段隔声量提升不明显,甚至在160 Hz、400 Hz、5...     

Impulse techniques for the simplification of insulation measurement between dwellings

This paper describes a novel method of measuring sound insulation in frequency bands or dB(A) using pistol shots as the source. The method has the advantages of speed and economy in comparison with classical measurements. Comparisons of the impulsive and classical methods are given for a number of structures and it is shown that the agreement is generally good.     

Calculation of the sound transmission between dwellings by partitions and flanking structures

A calculation model is presented for the sound transmission between dwellings by partitions and by flanking structures, based on the application of classical theory.The most important data needed are the sound reduction index for direct transmission of the different structures and the vibration level differences across junctions. Information on the reduction index is given, based on theory, taking into account the influence of boundary conditions by means of the structural reverberation time in situ. The vibration level differences have been determined for different junctions on the basis of in situ measurements. Under some—reasonable—restrictions this model gives the same results as would be achieved by applying the so-called Statistical Energy Analysis (SEA).Comparison between calculation and measurement for seventy-five different situations shows good agreement, the average predictions being correct with a standard deviation of 1·5 dB.     

A databank of sound insulation measurements

An acoustic databank of sound insulation measurements is being compiled at the University of Liverpool. In this paper we discuss the necessity for, and advantages of, such a databank. The formation of the entries in the bank has been discussed and then classified under established concepts. The coding and the purpose of the parameters selected for the compilation of the databank is explained, and the uses intended for the databank given.The databank is expected to benefit the building industry as a whole, as well as research workers engaged in related problems.     

Comparison of outdoor microphone locations for measuring sound insulation of building facades

Measurement of the acoustical insulation of building facades requires simultaneous measurement of sound pressure levels indoors and outdoors, but there is still some question as to the best location for the outdoor microphone. This paper reports the differences between sound pressure levels at 2 m from a facade and at its surface, for a series of measurements at 33 different houses. The mean results compare well with a modified line source model, and suggest that a 3 dB correction between measurement locations is appropriate on average, except at low frequencies. The variation in the results, from house to house, suggests that establishing a single preferred outdoor microphone location is desirable.     

A new system for rating impact sound insulation

The rating of impact sound insulation on the basis of tapping machine measurements with the ISO reference values has proved to be unsatisfactory in practice. This is mainly due to the differences in spectrum shape of tapping machine noise and real life impact noises, such as walking. The problem can be solved by changing the reference values in accordance with these differences in spectrum shape. The difference between tapping and walking noise spectra has been established by measurements on 49 different floors. In the most important frequency range (125–500 Hz) it was discovered to be sufficiently constant for all the floor constructions considered.Thus a new set of reference values has been derived, based on the assumption that the NR-curves provide a correct subjective rating system for walking noise.In addition, due account has been taken of the different frequency content at higher frequencies of impact noises other than those made by walking males, such as those made by walking females, jumping children, the moving of furniture, etc.     

Field measurement of airborne sound insulation between rooms with non-diffuse sound fields at low frequencies

Procedures for the field measurement of airborne sound insulation between rooms with diffuse fields are described in International Standard ISO 140-4. However, many dwellings contain rooms with volumes less than 50 m³, where low frequency measurements are less reliable; hence there is a need for a measurement procedure to improve the reliability of field measurements in rooms with non-diffuse fields. Procedures are proposed for sound pressure level and reverberation time measurements for the 50, 63 and 80 Hz third octave bands. The sound pressure level measurement combines corner microphone positions with positions in the central region of each room. This provides a good estimate of the room average sound pressure level with significantly improved repeatability.     

Parameters influencing low frequency impact sound transmission in dwellings

As sound and vibration fields in dwellings exhibit modal behaviour at frequencies below 200 Hz, a systematic investigation of measurement and prediction uncertainty associated with impact sound transmission at low frequencies must include the effects of: location of the impact, type of floor, edge conditions, floor and room dimensions, room absorption and position of the receiver. Experimentally validated analytical models, described in a companion paper, have been used in an extensive investigation of impact sound transmission through rectangular homogeneous concrete floors and floating floors. The models were used to describe the effect of modal coupling and then to perform parametric and statistical studies aimed to identify the main factors affecting low frequency impact sound transmission.     

Relationship between sound insulation performance of walls and word intelligibility scores

Conversations must be shielded from people in an adjacent room if they include confidential information. Word intelligibility tests were performed in a total of 185 sound fields to examine the relationship between sound insulation performance and the degree of conversation leakage. The parameters of the test sound fields were background noise level in the adjacent room and the level difference between the two rooms. The background noise level was varied from 30 to 50 dB (A-weighted). The level difference was parametrically varied in terms of eight frequency characteristics and 10 absolute values. The results showed that word intelligibility scores were strongly correlated with the A-weighted speech-to-noise ratio and SNR_uni32. Equal-intelligibility contours, which can easily show the weighted level difference and A-weighted background noise level required to achieve a certain level of word intelligibility scores, were obtained from a multiple logistic regression analysis.     

住宅隔声的预测:计及侧向传声的简易方法

本文提出了一种预测房间隔声的方法，它考虑了侧向传声，而以容易得到有关于房屋布局，隔墙及其支撑的资料作为基础，分离了三种传声路长并作出解释，最后给出一些测量与计算之间相比较的例子。     

Measurement of sound insulation with a sound level meter

The present technique for measuring the airborne sound insulation of walls and floors, involving measurements in 16 one-third octave bands, is tedious and expensive. The method provides more information than is needed for most purposes, and is more suited to research.Several investigators have proposed the measurement of the overall A-weighted sound level difference using a sound level meter, with a broad band source of white or pink noise. Consistent results have been obtained but their relation to accepted rating methods such as STC is rather empirical.The reference curves used for airborne sound insulation, i.e. STC and HPGW are very similar to the A weighting curve, and if the latter were adopted as the reference curve, there would be a firm theoretical basis for measurement with a sound level meter. Measurement of the difference between the linear sound level of a source of white noise, and the A weighted received level, would in practice be a test of the conformity to the A weighting curve of the transmission loss curve of the partition. Adverse deviations would show as a higher received level. Favourable deviations would have little effect.A study of practical walls and floors, taken from National Building Studies Research Paper 33, showed that there was good correlation between the sound level difference calculated as if it had been measured directly with a sound level meter, and a proposed rating method similar to ISO R717, but using the A weighting curve as the reference curve. Ninety-six per cent of results were within ±1 dB.The practical difficulties of achieving a reasonably flat transmitted spectrum, and of correcting for room absorption will reduce this precision, but bearing in mind the practical success of other short tests, the proposed test should provide a rapid test which is adequate for approval purposes.