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Severe noise problems involving a small number of people can often be solved following a detailed examination of the factors involved. At very least, provided the necessary resources are available, the noise source and the offended people can usually be separated by distance or by sound insulation. More usually, however, real noise nuisance problems are very complex, involving trade-offs between the benefits of less noise and the costs of lessening it. It is clearly desirable to minimise the harmful effects of noise upon public health but how low must the limits be set and can the costs be met? In general the environmental planner is faced with two problems, firstly to predict the extent and severity of environmental noise impact and secondly to assess the acceptability, or otherwise, of this impact in some absolute sense. The second of these problems is perhaps the more difficult as its solution ultimately rests on the political question of how many affected people can be justified. But the first is of no less importance since the policy-maker must be able to make qualitative evaluations of the effects of different policy options. This paper examines the problem of environmental noise nuisance what it is and how it can be measured and predicted. Detailed methodology is beyond the scope of the paper which concentrates instead upon a discussion of the factors involved and the nature of the relationships between them.

A major survey of sound insulation between dwellings in modern constructions is being carried out by the Building Research Station. The results of this survey will provide information on the operation of a performance-based building regulation and should lead to improved predictions of sound insulation. Some preliminary results are given for the performance of party walls in timber-framed dwellings.

This paper presents a means of solving equations of the form used in statistical energy analysis of sound transmission. It deals with the calculation of the sound transmission for the case of several acoustic power sources placed in an arbitrary structure consisting of any number of rooms, separating panels and cavities, by using the statistical energy analysis (SEA). A set of simultaneous equations, which arise from the application of SEA to multiple path systems, can be obtained on a computer by using a particular algorithm. For this case, the sound pressure level in each room can be calculated. The method of calculation for the case of one acoustic power source, namely the calculation of the sound insulation, is explained as a special case. The general method of solution for one or several acoustic power sources is described. A simple matrix has been established for the generalized solution. Examples for using the generalized solution are given.

(1975). Tips on Shielding and Soundproofing. American Journal of EEG Technology: Vol. 15, No. 3, pp. 127-130.

Previous attempts to correlate lab and field sound‐insulation performance have been based on a comparison of the lab sound‐transmission class (STC) and the field sound‐transmission class (FSTC). In this study comparisons of the 1/3‐octave‐bandwidth transmission loss (TL) values are made taking into account partition transmission, flanking transmission, and test‐environment factors. An experimentally determined flanking TL is obtained through a quantitative relationship between the partition, flanking, and field TL. This determination allows separation of test environment factors related to diffuseness and modal distribution from flanking transmission. Also noted under field conditions are interactions between the coincidence phenomena and the sound field under absorptive room conditions (reverberation time = 0.5 sec), demonstrating that the properties of a partition depend in part on the dwelling‐unit furnishings. Because all the test‐environment effects observed resulted in TL values higher than those of...

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.

Bias ply truck tire resonant vibration and sound fields were evaluated in the laboratory by standard vibration and sound measurement procedures. Four resonances were isolated between 90 and 250 Hz. Analysis of the sound and vibration fields showed that each isolated resonant mode radiates acoustic energy like a simple source. The modes investigated were determined to be acoustically slow with the attendant acoustic radiation emanating from a region within ¼ wavelength of the tire footprint.

The insulation of partially open dual glazing has already been measured in the laboratory. During an extensive programme of sound insulation tests on a house near Manchester Airport the opportunity was taken to measure the field performance. The results show an increase in insulation of up to 3 dB(A) when compared with predictions based upon laboratory SRIs. An assessment was also made of the ventilation by comparing the rate of air change when the dual windows were open with that due to a mechanical ventilator operating with the windows closed. Under typical weather conditions it was found that there was little difference, a rate of 2–3 air changes/hour being measured.

A graph and an equation are presented for the ready evaluation of the required sound‐transmission loss at any frequency for each of several components of a composite sound barrier, to economically achieve a desired interior noise spectrum, given the spectrum of the exterior noise and the areas of each of the significant boundaries of a room. It is also established that for common automobile and jet aircraft noises, the necessary insulation of such exterior room boundaries is not well represented by an STC rating.

Current developments in V/STOL aircraft indicate that the predicted acoustical environment of passenger cabins is increasing. It is unlikely that conventional soundproofing treatments will be dramatically improved, and new soundproofing principles are needed. A method is described for achieving the same noise reduction, in the low frequency range below about 1000 c/s, as a conventional treatment, but with a radical saving in space, using an acoustic isolator-membrane structure. A range of isolators are studied experimentally to determine the most desirable combination of materials for isolator-membrane components. Further analysis and experiment is desirable to optimize the isolator-membrane principle in soundproofing.

This paper has been published in three consecutive issues of Applied Acoustics. This final part consists of the author's conclusions and findings and the tabulated data discussed in Part 2. A considerable amount of information has been collected which was not previously available in one paper and some areas in which more information is required have been indicated. An empirical equation relating the mean sound insulation of single glazing to glass thickness has been derived but this has not been possible for double glazing. The author concludes that the effects of isolating the panes of a double window and the design of openable double windows need to be examined in more detail. In addition, agreement as to which is the most appropriate method, diffuse or directional sound fields, for measuring the insulation of windows and other facade elements needs to be reached. A standard presentation of results, including full details of edge mounting, panel dimensions, frame construction, the properties of absorbent material used for lining the edges of the air space of double windows and an indication of the accuracy of the measured values ought, we feel, to be adopted. However, the results of laboratory measurements can only serve as a guide. The external sound field, the building construction and the amount of absorption in the room can all influence the effective sound insulation of a completed building. Further studies of the effects of these factors, particularly the first two, are necessary so that they can be taken into account at the design stage of a building. It is important that the sound insulation of windows should not be considered in isolation from the rest of a building. For example, if windows with good sound insulation are installed the internal partitioning should have an appropriately high sound insulation if distraction from internal noise sources is to be avoided. The ultimate success of the acoustical environment of a building depends on the satisfaction of the building's occupants, therefore, objective measurements should be supplemented by subjective studies. The cost of the various methods of improving sound insulation must also be related to their subjective benefits.

A method is evolved for predicting the transmission loss of soundproofing multiple‐element configurations containing any number of elements. The optimum distribution of mass between the impervious elements (fuselage skin panel, blanket septa, trim panel) is determined for a general theoretical configuration and for a typical aircraft structure. The theoretical improvement obtained by mass distribution optimization (approximately uniform distribution between the impervious elements) is about 3 to 6 dB in the low frequencies (below 500 cps) and 8 to 14 dB in the speech interference range (600 to 4800 cps).It is shown that a large increase in air spaces between elements is required to obtain only about 8‐ to 10‐dB improvement (in theory), neglecting contact flanking paths between the elements. Also, replacing air spaces with acoustical blankets produces small improvements (2 to 8 dB) at the cost of possible structural flanking transmission between the elements.It is also shown that covering a hard terminatin...

This paper deals with the hovercraft noise problem from two distinct points of view. At the outset, hovercraft noise is reviewed in relation to the noise associated with other means of transport. While hovercraft appear to be rather less noisy than aircraft of comparable installed power, they tend to be much noisier than conventional surface transport. It is concluded that, for the first generation of commercial craft, the distance between a terminal and the nearest houses in a quiet residential area should be at least 800 yd to completely avoid increase in the normal level of noise. On the other hand, in a busy urban locality, a distance of 150 to 200 yd is sufficient to bring the noise from the hovercraft down to the existing level of traffic noise. Estimates made in connection with the design of the SR.N 4 show that these distances will be substantially reduced for the next generation of hovercraft. It is pointed out that the noise problem at a terminal can be alleviated by minimizing the need for manoeuvring. The sources of hovercraft noise and the means for their reduction are then discussed. The external noise from existing hovercraft is dominated by that originating from the propeller and attention is drawn to the fact that actual measurements reveal that this noise is appreciably higher than would be expected from theoretical predictions. It is considered that reduction of the tip speed is the most effective way of reducing propeller noise. Large numbers of blades and the use of devices such as shroud rings are rejected as either ineffective or actually detrimental. For turbo-shaft engined hovercraft, compressor noise usually ranks next to propeller noise in importance. However, noise from this source can be reduced by muffling the air intakes. Noise from lifting fans is relatively unimportant at present but, as developments reduce the level of propeller and engine noise, it could become significant and thus merits attention. Inside a hovercraft, transmission and engine noise are usually predominant. However, the high frequencies involved can be dealt with quite effectively by aircraft soundproofing techniques and there are few fundamental problems involved.

Most of the world's major nations, with the exception of the United States of America, have sound‐insulation requirements in their building codes. The purpose of this paper is to describe the experience of several European countries with such requirements. Typical procedures in common use are discussed: there are several variations in the basic definition of sound insulation, the method of interpreting test results, and, finally, the method of influencing or controlling building practice. An important consideration is the information to be gained from various possible types of test. Experience indicates the desirability of three stages of testing for a new type of construction: (1) laboratory tests on individual components; (2) tests on a partial assembly of wall and floor sections; and (3) tests on the completed structure. At each stage, problems are usually found that had not been anticipated earlier.

The measurement of the sound insulation of two adjacent rooms, according to the ISO recommendations, is based on the determination of the sound level, assuming the sound field to be sufficiently diffuse, at different points of the two rooms, at a given distance from the walls. In some cases, for particular requirements of quiet (in bedrooms) or of privacy (in offices or telephone booths), it may be useful to investigate the sound field in the listening room in proximity of the partition, or even in contact with the partition itself. Results are reported of laboratory measurements for some kinds of partitions, evaluating particularly the variation of transmission loss in the proximity of the partition itself. These results are accompanied by determinations of acceleration by means of a vibration-meter, on the partition when excited by the sound field of the source room. From the above results it is possible to deduce the variation of intelligibility of words uttered in the source room, as a function of the distance of the listening point from the partition wall. Considering the case of a listener whose ear is in contact with the partition, the data of acceleration measured are correlated with the results of subjective determinations in similar listening conditions. These results suggest an investigation of the possibility of evaluating the privacy of two rooms on the basis of data relative to the examined partition.

Some types of lining used on internal wall surfaces of buildings have been found to influence sound insulation. This effect is due to the excitation of mechanical resonances in the lining. There is insufficient evidence available from which to make specific proposals, but it is recommended that where resilient linings are used, consideration should be given to the possible acoustic consequences.

It is, on occasions, of advantage to determine the sound insulating properties of a partition material from a small sample or to measure the sound transmission through a new form of construction before the building of which it is part is complete. Under these conditions, conventional sound insulation measurements are not possible and specialized techniques have been employed to obtain results. The predictions made by these techniques have been found to agree well among themselves, with theoretical results, and with conventional measurements where these have later been possible. The limitations of the methods are mentioned.

In a sound field the head is set into forced vibrations, and the vibrations are sometimes heard by bone conduction. For clinical purposes it is important to know the magnitude of these vibrations of the head so that, in cases of partial deafness, the roles of air conduction and bone conduction can be understood.The pattern of the head vibrations and the velocity of the deformation waves traveling along the bony wall of the skull were measured. For the velocity we found c = 570 m/sec. In the course of the experiments, a new method of calibrating a vibration pick‐up with a sound level meter was developed.It was found possible to construct an earphone that reduces the amount of “cross‐hearing” to a very low value. With this earphone, hearing thresholds can be measured in many cases without using noise to mask the ear with the better hearing, even though the difference between the sensitivities of the two ears is greater than 40 db.It is shown that the maximal sound insulation that can be obtained with an ear...

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.

This paper describes a sampling and averaging technique developed for the averaging of several fluctuating microphone signals. Its use has considerably shortened the time taken to carry out measurements of airborne sound insulation and the technique may have applications in other fields.

The noise level produced by a fan was reduced by 21 dB(A) by enclosing it in a ‘soundproof box’. The general problems of designing such a box, and, in particular, that of preventing the enclosed fan from overheating, are discussed. The construction of the box is described in detail and its actual performance compared with that theoretically attainable.

In this paper we consider the problem of measuring the loss factors of large panels, particularly when their damping is high. A method of measurement which may be used over a wide range of damping values is described. It is shown that it is important to measure the damping of panels and walls in situ since the damping can depend critically on the mounting conditions used and is often greater than the internal damping of the wall material itself. It is suggested that a measurement of damping should be made whenever the sound insulation of a panel or wall is measured in the laboratory.

The subject of the paper is related to a method of measuring the transmission of sound through partitions. Equations have been derived for the decay of reverberant sound in each of two chambers con...

The maximum distance at which an airplane in flight may be detected by aural listening through sound locators has been found to depend on the ambient or masking noise level. Ambient noises and local disturbances which contribute to increase noise level at the listener's ear were investigated. Contrast between ambient sound and that of the airplane, either as total sound or some part of the sound frequency spectrum, rather than degree of amplification of the combined sound of the airplane and ambient through the sound receiver determines audibility. There are many disturbing elements which affect sound locator range. Some are generated within the sound locator receiver and mounting structure. Their magnitude and effect increase the masking sound level at the listener's ear and considerably reduce range. Soundproofing sound receivers, their mountings and cooperating units reduces the disturbance. The distortion of sound when amplified was studied. Since range was not dependent on amplification a smaller rec...

The best method of noise control is elimination of the noise at its source by modification of the noise producer; in certain cases this may not be possible since the normal functioning of the noisy device would be impaired. Alternatively the source may be enclosed, either completely or partially so as to shield the observer from the source. A third method involves the treatment of surfaces in the room containing the observer and noise source to absorb the noise as it is propagated through the room. Finally the observer, or at least his ears, may be enclosed by a soundproof booth or the wearing of ear defenders. Examples of the successful quietening of pieces of machinery will be discussed, including the couch roll of a paper making machine. A reduction of 15–20 decibels in sound pressure level has been achieved without interference with the paper making qualities of the roll.

In order to get a better insight into the variation in the insulation of a number of specimens of the same construction, some series of measurements have, over a period of years, been carried out for various constructions. Different ways of interpreting the measured results will be mentioned. At the request of the Dutch Foundation for Building Research a similar but more extensive investigation is now in progress, carried out in co-operation with the Sound Division of the Technical Physics Department T.N.O. & T.H.

General noise reduction considerations for shipboard installation of gas turbines are discussed. Specific information relating to sound-absorption materials, duct treatments, structureborne sound isolation, and airborne sound insulation is graphically presented.

In principle, the new Dutch code (NEN-1070, December 1962) is closely related to the German one as far as airborne and impact sound insulation is concerned. A simplification is that requirements are formulated for four octave bands only. On the other hand, an additional requirement is included, which restricts unfavourable deviations from the standard values. The decision to conform more or less with the German code was based on the results of an analysis of radio programmes. A survey of this work is given. Sound insulation requirements in the Dutch code relate to the sound insulation between two rooms in adjacent dwellings, not to the sound insulation of walls or floors as such. This means that flanking transmission has to be taken into account. Some directives in this respect are incorporated in the code. Apart from sound insulation, requirements are formulated for a number of other possible noise sources, as, for example, the reverberation in staircase halls, sanitary installations, slamming doors, etc. These have been viewed partly from quantitative and partly from qualitative standpoints.

Suggestions are made pertaining to standard methods of measuring the sound absorption of acoustical materials and the sound transmission loss (STL) of partitions. (1) Concerning the reverberation chamber method of measuring the sound absorption of materials, it is shown that the absorption varies with the position of the sample in the chamber, owing to interference patterns. An estimate is made of the difference in absorption of a sample on the floor (a) centrally and (b) touching one side wall. It is suggested that sample position should be specified as distant at least half a wavelength (λ/2) from walls and reflecting surfaces other than the one backing the sample. (2) Regarding the measurement of STL it is suggested that microphone position be specified as at least λ/2 from walls and the corresponding distances from edges and corners of reverberation chambers. The technique in which the microphone is placed near a wall is not recommended. (3) As a single figure for the over‐all sound insulation value of a partition, the arithmetic mean of the decibel STL figures at various frequencies is often used. It is suggested that a better average figure is obtained if the linear ratios corresponding to these decibel figures are averaged instead of the decibel figures themselves. This removes the logarithmic weighting of the latter average, for which there is no physical justification.

A survey is made of past and present systems for rating the sound‐insulation value of building walls and floors. It is observed that in most countries ratings based on “average” transmission losses have been replaced by systems that compare transmission‐loss characteristics with a standard contour. An example of this approach is the new sound‐transmission class contained in ASTM E90‐61T. This is discussed from various theoretical and practical viewpoints, and it is concluded that the sound‐transmission class is a useful rating system for common architectural problems.

This paper is to be published in three consecutive issues of Applied Acoustics . This first part is a brief survey of the theory and practice of the measurement of the sound insulation of glass. In Part 2 the effects of changes in the various parameters will be discussed. The tabulated data supporting this discussion will constitute the final part. With the increase of noise in the external environment more attention is being focussed on the need for better sound insulation of buildings. If high sound insulation is required, the window and its design become important. Although results of sound insulation measurements obtained in the laboratory are not strictly comparable with the values achieved in actual buildings, laboratory measurements are necessary as a basis for design decisions. There is a need for a review of the currently available results of such measurements which this paper is intended to provide. The theoretical aspects of the sound insulation of both single and double panels are briefly outlined but the major part of this paper is concerned with the presentation of the results obtained by various experimenters. Recommendations as to which window construction should be used for protection against a specific noise, such as traffic noise or aircraft noise, are not made, since this would require a discussion of the subjective aspects of noise, which is outside the scope of the present work.