Noise from neighbours and the sound insulation of party walls in houses

Nine-hundred-and-seventeen residents in a sample of attached houses constructed since 1970 were interviewed in the course of a national survey dealing with nuisance occasioned by noise from neighbours. The airborne sound insulation of the party walls, measured prior to occupation, ranged from zero to 120 dB AAD. Two-thirds of the respondents heard noise from their neighbours and even at performance levels meeting or exceeding the minimum requirements of the Building Regulations nearly 50% did so. Of the total sample, some 18% were seriously bothered by neighbours' noise. Highly significant relationships were found between physical performance rated in dB AAD (Aggregate Adverse Deviation) and a variety of subjective responses. These include reports of hearing neighbours' noise, of being bothered by it, hearing neighbours' conversation, and, in particular, the direct rating of sound insulation quality by respondents, which last appears to provide the most reliable and consistent indication of the likelihood of experiencing nuisance from neighbours' noise. These results provide, for the first time, empirical validation of the U.K. performance rating procedure. In addition, the survey findings emphasize the importance of impact noises, not included in the standardized performance measurements, but which contribute substantially to nuisance, particularly between houses where airborne sound insulation is comparatively good. Other findings indicate that occupants were very satisfied with their general environment and only slightly less so with their homes. Poor sound insulation was a prominent criticism of the dwellings, being ranked third among spontaneous adverse comments and first in a ranking of nine commonly encountered building defects. These results indicate the importance of sound insulation to occupants of recently built houses, placing this aspect of design and construction within a wider context. The overall results of the survey provide a practical guide to estimating the consequences, in terms of occupants' attitudes to noise from neighbours, of raising or lowering standards of sound insulation performance between houses.     

Noise-impact estimates per FTA and APTA criteria

In a recent paper, light-rail line noise exposures were predicted both in terms of maximum pass-by sound levels for comparison to APTA criteria and day-night average sound levels for comparison to FTA criteria. For the local land uses and ambient noise conditions of the project, the distances for the unmitigated pass-by noise exposures to attenuate to the APTA and FTA criteria limits were estimated and the numbers of included dwellings counted. The results found that the FTA impact-onset (i.e., “some-impact”) criterion curve yielded significantly greater noise exposed areas while the APTA criteria yielded results between those of the FTA “some”- and “severe”-impact curves. However, those results only applied to the specific project under evaluation. This paper attempts to extend and generalize the comparison by parametric computation of exposed areas using both the FTA and APTA procedures. Predicted exposures in this paper are compared as a function of background ambient sound levels, type of land use impacted, numbers of daytime and nighttime operations, and train pass-by maximum sound levels. At very low background ambient sound levels, FTA tended to predict the greatest exposure, while in very noisy environments, APTA predicted more exposure. APTA predicted more exposure with low numbers of daily and/or nighttime operations, and FTA predicted more exposure with high numbers, but the comparative exposures were strongly dependent upon background ambient sound level and land use. For train pass-by maximum sound levels, APTA tended to show more exposure for very quiet pass-bys and to be intermediate to FTA/some and FTA/severe for noisier events—with the comparative exposures strongly dependent upon background ambient and land use.     

EURailNoise: a study of European priorities and strategies for railway noise abatement

The European Union is developing its noise policy by using a number of expert groups on specific noise issues. One of the most relevant noise problems is railway traffic which is dealt with by Working Group 6 (WG 6). The Commission of the European Union appointed a consortium of six consultants and experts in railway noise to prepare a study on European priorities and strategies for railway noise abatement. The main purpose of this study was to support the work within WG 6 and to create an inventory of measures for future railway noise abatement policy of the European Union. The EURailNoise study was to be completed in autumn 2001. The countries included the European Union member states, together with Norway, and Switzerland, and three prospective members (Hungary, the Czech Republic, and Poland).The EURailNoise study consisted of three main parts. The baseline was a review of current European legislation on railway noise generation as well as noise perception. In parallel a documentation of cases, where technical measures against railway noise had been successfully applied, was prepared using a classification of “good practice”, “promising new technology”, and “promising research results”.The second part covered the potential for further noise reduction demonstrated for High Speed Passenger Traffic, S-Trains, Locomotives, Trams, Freight Traffic, Track Design and finally Wheels and Track Monitoring and Maintenance. Thirdly, a strategy for future activities of the Commission concerning the reduction of rail noise was to be proposed including a proposal for noise emission limits. This paper summarizes the results of the EURailNoise study.     

Relationship between loudness perception and noise indices in Valdivia, Chile

Residents perception of road traffic noise loudness in relation to the measured noise indices close to their dwellings was studied. Percentile distributions of five loudness categories as a function of the Day-Night noise index L_DN were obtained. Hearing sensitivity was considered as a factor in loudness perception. In addition, the prevalence of people’s perception of traffic noise in the “Extremely Loud” loudness category was compared with percentage of people stating that they were “Highly Annoyed” by noise. It is concluded that hearing sensitivity for noise is one of the variables that explains the loudness classification difference in different L_DN index ranges and that the percentages of people “Highly Annoyed” by noise are slightly higher than the percentages obtained in the “Extremely Loud” category of loudness perception.     

A survey of the sound insulation between dwellings in modern building constructions

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.     

Sound radiation from inflow turbulence in axial flow fans

The sound radiated when inflow turbulence is present in axial flow fans has been investigated. Theoretically, two noise radiating mechanisms can be identified: (i) interaction of turbulence with the rotor potential field results in a quadrupole-type volume source distribution, producing “flow-interaction” noise; (ii) impingement of turbulence on the blades results in a dipole-type (fluctuating force) surface source distribution, producing “fluctuating lift” noise. A theoretical expression for the flow interaction sound power in the upstream radiation field has been developed, in terms of parameters that can be experimentally determined by near field flow measurements involving spatial cross-correlations of the fluctuating axial velocity, with respect to both radial and circumferential position. Both these measurements and radiated sound pressure measurements have been made for eight- and ten-bladed rotors of relatively low tip Mach number (< 0·3). The sound pressure measurements revealed the occurrence of band-spreading of discrete tones at the blade passing frequency and its harmonics, as would be theoretically predicted for quadrupole-type sources here. The theoretical predictions and the measurements, respectively, of the sound power radiated upstream were compared. The results indicated that, for the fans tested, the “fluctuating lift” noise strongly predominated over the “flow-interaction” noise. The observed sound power levels were consistent with levels estimated from the theory.     

Aeroacoustics research in Europe: The CEAS-ASC report on 2010 highlights

The Council of European Aerospace Societies (CEAS) Aeroacoustics Specialists Committee (ASC) supports and promotes the interests of the scientific and industrial aeroacoustics community on an European scale and European aeronautics activities internationally. In this context, “aeroacoustics” encompasses all aerospace acoustics and related areas. Each year the committee highlights some of the research and development projects in Europe.This paper is a report on highlights of aeroacoustics research in Europe in 2010, compiled from information provided to the ASC of the CEAS.At the end of 2010, project X-NOISE EV of the Seventh Framework Programme of the European Commission has been launched as a continuation of the X-Noise series, with objectives of reducing aircraft noise and reaching the goal set by the ACARE 2020 Vision.Some contributions submitted to the editor summarizes selected findings from European projects launched before or concluded in 2010, while other articles cover issues supported by national associations or by industries. Furthermore, a concise summary of the workshop on “Aeroacoustics of High-Speed Aircraft Propellers and Open Rotors” held in Warsaw in October is included in this report.Enquiries concerning all contributions should be addressed to the authors who are given at the end of each subsection.     

Aeroacoustics research in Europe: The CEAS-ASC report on 2009 highlights

The Council of European Aerospace Societies (CEAS) Aeroacoustics Specialists Committee (ASC) supports and promotes the interests of the scientific and industrial aeroacoustics community on an European scale and European aeronautics activities internationally. In this context, “aeroacoustics” encompasses all aerospace acoustics and related areas. Each year the committee highlights some of the research and development projects in Europe.This paper is a report on highlights of aeroacoustics research in Europe in 2009, compiled from information provided to the ASC of the CEAS.In April 2009, the Level-2 project OPENAIR of the Seventh Framework Programme of the European Commission has been launched with the goal of delivering a step change in noise reduction, beyond the successful achievements of the predecessor SILENCE(R).Some contributions submitted to the editor summarizes findings from programmes launched before 2009, while other contributions report on activities supported by national associations and industries. Furthermore, a concise summary of the workshop on “Resolving Uncertainties in Airframe Noise Testing and CAA Code Validation” held in Bucharest is included in this report. Enquiries concerning all contributions should be addressed to the authors who are given at the end of each subsection.     

Standardised acoustic characterisation of sonic crystals noise barriers: Sound insulation and reflection properties

This work presents sound insulation and sound reflection measurements conducted over sonic crystal noise barriers according to the European standards EN 1793-2, EN 1793-5 and EN 1793-6. In most of the reference literature, sound insulation and reflection properties of sonic crystals are measured or a diffuse sound field or in a direct sound field including the top and side edge diffraction effects together with the transmitted (or reflected) components. The aim of this work is to perform free-field measurements over a real-sized sample in order to window out all diffraction components and to verify the points of strength and weakness of the application of standardised measurements to sonic crystals. Diffuse field measurements in laboratory are also done for comparison purposes. Since the target frequency range for traffic noise spectrum is centred at around 1000 Hz, a finite element based parametric investigation is performed to design unit cells capable of generating band gaps in the one-third octave bands ranging from 800 Hz to 1250 Hz. Then, 3 × 3 m sonic crystal noise barriers are installed in the Laboratory of the University of Bologna and sound insulation and sound reflection measurements are performed according to the mentioned active standards for normal incidence. Sound insulation is measured for diffuse incidence too. The two methods give different results. The method more directly comparable to calculations is the free-field one. However, if on the one hand the application of a time window allows to compute the transmitted or reflected component only, on the other hand the time window itself limits the maximum width of the sample for which all reflections of the n-th order having a significant spectral content are included, and thus results critical in the analysis of this kind of noise barriers. Nevertheless, the standardised measurements allow a direct comparison between the performance of sonic crystals and common noise barriers.     

Vibro-acoustic analysis procedures for the evaluation of the sound insulation characteristics of agricultural machinery cabins

Over the last few years, customer demands regarding acoustic performance, along with the tightening of legal regulations on noise emission levels and human exposure to noise, have made the noise and vibration properties into important design criteria for agricultural machinery cabins. In this framework, both experimental analysis procedures for prototype testing as well as reliable numerical prediction tools for early design assessment are compulsory for an efficient optimization of the cabin noise and vibration comfort.This paper discusses several numerical approaches, which are based on the finite element and boundary element method, in terms of their practical use for airborne sound insulation predictions. To illustrate the efficiency and reliability of the various vibro-acoustic analysis procedures, the numerical procedures are applied for the case of a harvester driver's cabin and validated with experimental results.     

A GIS based road traffic noise prediction model

A road traffic noise prediction model has been developed suitable for use in China. This model is based on local environmental standards, vehicle types and traffic conditions. The model was accurate to 0.8 dBA at locations near the road carriage way and 2.1 dBA within the housing estate, which is comparable to the FHWA model. An integrated noise-GIS system was developed to provide general functions for noise modeling and an additional tool for noise design, where a new interaction mode in “WHAT IF Question/Explanation” format was used. Application of this system offered improvements in the efficiency and accuracy of traffic noise assessment and noise design.     

Establishing a new acoustical laboratory, planning, experiments, experiences

A significant part of the input data for planning the acoustical quality of building is the result of laboratory measurements. Detailed modelling of complex phenomena of sound transmission, like structure borne sound propagation can be solved based on on well planned laboratory experiences. However it seems the constructional details of the testing facilities have important effect on the measured results. The paper describes the process of planning the testing facilities of the Laboratory of Building Acoustics, TU Budapest, which operate as a standardised laboratory, a modelling “tool” for flanking transmission in research and development and which is utilised in teaching too. Some results and conclusions of recent experiments are also reported and discussed here related to the sound reduction index of a heavy brick wall without and with flanking transmission, to the impact sound insulation between the rest of a stair and an adjacent room and also to a possibility to determine the reduction of impact sound transmission of floor coverings.     

Vibration in dwellings from road and rail traffic — Part III: towards a common methodology for socio-vibrational surveys

While a range of international standards defining noise, vibration and other physical environmental measures have been established, common methodologies for measuring people's reactions to these same environmental effects are still in their infancy. This reduces the comparability of prevalence statistics and exposure-effect relationships developed by different researchers. The public authorities are served incompatible or seemingly conflicting information from different surveys when deciding on appropriate guidelines and limits. Drawing on experiences with the 1998 Norwegian Socio-vibrational Survey and a Swedish socio-acoustic survey supplemented with vibration measures, a new Nordtest Method: NT ACOU 106 Acoustics—Assessment of annoyance by vibrations in dwellings from road and rail traffic has been defined. The method describes sampling requirements, and proposes a mandatory verbal 5-point categorical annoyance scale and an optional 11-point numerical annoyance scale, both with lower anchoring point “Do not notice”. A survey data output format is specified to allow researchers to pool data from different surveys.     

Noise control measures in the new Singapore International Airport

This paper describes some of the noise control measures incorporated in the passenger terminal building at the new Singapore International Airport at Changi. As the acoustics adviser to the Changi Airport Development Division of the Public Works Department, the overall consultant of this multi-billion dollar project, the author reviews some of the special steps taken to incorporate some of the latest acoustics techniques in this airport.These include the establishment of norms for various factors such as permissible background noise levels to each of the rooms, offices, arrival and departure halls, etc. Specifications called for include optimum sound absorption and reverberations times, airborne sound insulation for internal and external building partitions and structureborne sound insulation, as well as a sophisticated sound reinforcement system.Because of the stringent requirements following some of these specifications, the factor of the skill and workmanship of the contractors involved in the erection of the partitions had to be allowed for. As a result, all suppliers and contractors were requested to send their building proposals for testing. This was done in the newly established Acoustics Laboratory of the National University of Singapore at Kent Ridge. Some of the tests carried out, based on International Standards ISO R140 and ASTM E90 on sound transmission loss and ISO R354 and ASTM C423 on sound absorption, are evaluated.     

Determination of the sound energy level of a gunshot and its applications in room acoustics

In some cases an impulsive noise source such as a gunshot can be a preferred alternative when investigating building acoustics, including sound insulation measurements, when compared to conventional steady state noise sources. A gun equipped with blank cartridges is an impulsive noise source that is lightweight and small enough to be easily transported. The differences in the noise characteristics between individual cartridges for the same gun are usually small, so the impulsive source can be replicated to a high degree. This paper is focused on the practical application of the sound exposure levels produced by a gunshot with a known sound energy level in the rooms under investigation. In this way, the equipment and methods required by the conventional method are simplified significantly. Furthermore, reverberation times need not be measured, since the equivalent absorption area can be directly obtained from the measured sound exposure levels. Using Green’s theorem, the roles of the sound source and measuring microphone were exchanged, which simplified the determination of sound insulation as it was easier to change the position of the gun than the microphone. The results obtained using the impulsive noise source were in good agreement with those obtained using the conventional method. Above 100 Hz, their difference in any frequency band of interest was less than 1 dB.     

Acoustic insulation capacity of Vertical Greenery Systems for buildings

Vertical Greenery Systems (VGS) are promising contemporary Green Infrastructure which contribute to the provision of several ecosystem services both at building and urban scales. Among others, the building acoustic insulation and the urban noise reduction could be considered. Traditionally vegetation has been used to acoustically insulate urban areas, especially from the traffic noise. Now, with the introduction of vegetation in buildings, through the VGS, it is necessary to provide experimental data on its operation as acoustic insulation tool in the built environment. In this study the acoustic insulation capacity of two VGS was conducted through in situ measurements according to the UNE-EN ISO 140-5 standard. From the results, it was observed that a thin layer of vegetation (20–30 cm) was able to provide an increase in the sound insulation of 1 dB for traffic noise (in both cases, Green Wall and Green Facade), and an insulation increase between 2 dB (Green Wall) and 3 dB (Green Facade) for a pink noise. In addition to the vegetation contribution to sound insulation, the influence of other factors such as the mass factor (thickness, density and composition of the substrate layer) and type of modular unit of cultivation, the impenetrability (sealing joints between modules) and structural insulation (support structure) must be taken into account for further studies.     

Annoyance and self-reported sleep disturbances due to structurally radiated noise from railway tunnels

In Norway, the requirement for structure borne noise from tunnels is L_pAFmax = 32 dB inside dwellings. According to the Norwegian Standard 8175 it is expected that up to 20% of the exposed population are disturbed by the noise at this level. However, the scientific basis for this noise limit is poor. The aim of this study was to determine the degree of annoyance and self-reported sleep disturbances as a function of L_pAFmax. In the present study, 521 dwellings exposed to structural sound from railway rock-tunnels were identified. A questionnaire was sent to one randomly selected person above 18 years of age from each dwelling. The results showed that both noise induced annoyance and reported sleep disturbances were significantly related to L_pAFmax. Other factors that increased the annoyance were high pass-by frequency of freight trains per day, and degree of sound insulation of the windows. At L_pAFmax = 32 dB, 20% were slightly or more than slightly annoyed, and 4% were moderately or more than moderately annoyed. According to the pre-existing assumption that up to 20% of the exposed population are disturbed by the noise at this level, the present results give support to the Norwegian noise limit L_pAFmax = 32 dB inside dwellings of structure borne noise from railway tunnels.     

Development of a 3D finite element acoustic model to predict the sound reduction index of stud based double-leaf walls

Building standards incorporating quantitative acoustical criteria to ensure adequate sound insulation are now being implemented. Engineers are making great efforts to design acoustically efficient double-wall structures. Accordingly, efficient simulation models to predict the acoustic insulation of double-leaf wall structures are needed. This paper presents the development of a numerical tool that can predict the frequency dependent sound reduction index R of stud based double-leaf walls at one-third-octave band frequency range. A fully vibro-acoustic 3D model consisting of two rooms partitioned using a double-leaf wall, considering the structure and acoustic fluid coupling incorporating the existing fluid and structural solvers are presented. The validity of the finite element (FE) model is assessed by comparison with experimental test results carried out in a certified laboratory. Accurate representation of the structural damping matrix to effectively predict the R values are studied. The possibilities of minimising the simulation time using a frequency dependent mesh model was also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index R_w along with A-weighted pink noise C and A-weighted urban noise C_tr within an error of 1 dB. The model developed can also be used to analyse the acoustically induced frequency dependent geometrical behaviour of the double-leaf wall components to optimise them for best acoustic performance. The FE modelling procedure reported in this paper can be extended to other building components undergoing fluid–structure interaction (FSI) to evaluate their acoustic insulation.