Sound Insulation Measurements Research Articles

Numerical Investigation of the Repeatability and Reproducibility of Laboratory Sound Insulation Measurements

An extensive parametric study has been carried out with a wave based model to numerically investigate the fundamental repeatability and reproducibility of laboratory sound insulation measurements in the frequency range 50-200 Hz. Both the pressure method (according to ISO 10140-2) and the intensity method (according to ISO 15186-1 and ISO 15186-3) are investigated. The investigation includes the repeatability of the different measurement procedures, which depends on the influence of the microphone positions and the source position. The reproducibility of the sound insulation measurements in different test facilities is studied by looking at the influence of geometrical parameters like room and plate dimensions, aperture placement and aperture thickness. The results show that for small-sized test elements, the reproducibility of the intensity method is better. For heavy walls and lightweight double constructions, however, the predicted uncertainty is similar for the three measurement methods. The results of the reproducibility study are also used to investigate systematic differences between the pressure method and both

In-situ measurements of sound reflection and sound insulation of noise barriers: Validation by means of signal-to-noise ratio calculations

After some years from its first release, the CEN/TS 1793-5 European standard for in-situ measurement of sound reflection and airborne sound insulation characteristics of noise barriers has been significantly enhanced and validated in the frame of the EU funded QUIESST project. The procedure, based on impulse response measurements near the noise barrier and in the free field, is robust and easily applicable but much attention must be paid when: (i) applying the signal subtraction technique to get the reflected signal component and (ii) extracting the transmitted component, especially measuring highly insulating noise barriers. In both cases, it is essential to avoid a poor signal-to-noise ratio of the critical part of the impulse response. In the frame of the QUIESST project specific quality criteria, applicable on site, have been introduced in order to check and validate the result. These criteria are rigorously described here for the first time and illustrative examples are presented.

Uncertainty analysis by a Round Robin Test of field measurements of sound insulation in buildings: Single numbers and low frequency bands evaluation - Airborne sound insulation

The uncertainty of field measurements of a lightweight wall and a heavy floor was analysed by Round Robin Test (RRT), conducted in a full-scale experimental building at ITC-CNR. Each of the 9 teams involved in the I-RRT replicates the tests 5 times, for a total of 45 measurements, while the repetitions of reverberation time were 110. Both for sound insulation and reverberation time the main variations are in the low frequency range. The differences between D, R', Dn and DnT and their reproducibility and repeatability standard deviations values were also analysed. The study is also focused on the single numbers evaluation: true value and uncertainty. Single numbers were evaluated in both narrow and extended range. The extension to low frequencies implies a variation in single number values that reaches its maximum in the case of X +Ctr in the extended range. This is because this index is the most influenced by low frequencies. Thus the measurement uncertainty at low frequencies has to be more deeply investigated, before including the low frequency range in the on-field measurements

Advancements in Sound Reflection and Airborne Sound Insulation Measurement on Noise Barriers

The in-situ measurement of sound reflection and airborne sound insulation characteristics of a noise barrier in Europe are currently performed following the CEN/TS 1793-5 European standard guidelines (last revision published in 2003 [1]). After some years a large number of barriers measured, the original method has been significantly enhanced and validated in the frame of the EU funded QUIESST project, WP3 [2]. The sound reflection measurement method has been improved using a square 9-microphone grid not rigidly connected to the loudspeaker, an optimized alignment algorithm of free-field and reflected impulse responses, including fractional step shifts and least squares estimation of the best relative position, and a correction for geometrical divergence and sound source directivity. Each single measurement is then validated by means of the Reduction Factor calculation. The airborne sound insulation measurement method has not been markedly changed since 2003, because the procedure is robust and easily applicable as it is, but some problems may still be encountered when measuring highly insulating noise barriers, due to a poor signal to noise ratio of the transmitted impulse response. In those cases it is difficult to realize just after the measurement whether the obtained data are valid or not. A method, applicable on site, to overcome this problem is described here. It is based on the Signal to Noise Ratio estimation of critical parts of the acquired impulse responses and gives a strong validation criterion.

The position of the intruments for the sound insulation measurement of building facades: From ISO 140-5 to ISO 16283-3

The international standard ISO 140-5 for the measurement of the sound insulation of building facades will be replaced by the new standard ISO 16283-3 soon. Together with solving a few limits of the existing standard, the review is going to introduce the procedures for measurements at low frequencies. This paper investigates the uncertainties related to the position of the instruments in sound insulation measurements of building facades. The positions proposed by the international standard ISO 140-5 are compared with those proposed in other standards and with the draft standard prISO 16283-3. The limits of measurement of the sound pressure level in front of the facade are investigated by comparing different placements both of the external source and the receiver. This shows that the average among different measurements is necessary in order to reduce the effect of interferences. The average of the sound pressure levels in different microphone positions is easier than the average obtained by movements of the loudspeaker. Later, different placements of the receiver inside the rooms are compared. In particular, corner and center room positions are assessed and their energy-average values according to the ISO 16283-1 are considered. Finally, the uncertainties related to equipment positions are discussed and suggestions to improve the future ISO 16283-3 are reported

The position of the intruments for the sound insulation measurement of building facades: From ISO 140-5 to ISO 16283-3

The position of the intruments for the sound insulation measurement of building facades: From ISO 140-5 to ISO 16283-3

Pressure Level Standard Deviation at Low Frecuencies: Effect of the Wall Vibrational Field

Abstract Knowledge of the uncertainty of measurement of testing results is important when results have to be compared with limits and specifications. In the measurement of sound insulation following standards ISO 140-4 and 140-5 the uncertainty of the final magnitude is mainly associated to the average sound pressure levels L1 and L2 measured. However, the study of sound fields in enclosed spaces is very difficult: there are a wide variety of rooms with different sound fields depending on factors as volume, geometry and materials. A parameter what allows us to quantify the spatial variation of the sound pressure level is the standard deviation of the pressure levels measured at the different positions of the room. Based on the analysis of this parameter some results have been pointed out: we show examples on the influence of the microphone positions and the wall characteristics on the uncertainty of the final magnitudes mainly at the low frequencies regime. In this line, we propose a theoretical calculus of the standard deviation as a combined uncertainty of the standard deviation already proposed in the literature focused in the room geometry and the standard deviation associated to the wall vibrational field.

An experimental study on the effect of rolling shutters on the field measurements of airborne sound insulation of façades

The façade is the visible part of a building, and generally consists of various different constructive systems. The sound reduction index of the closing elements for the openings on a room’s façade is a determining factor in the sound insulation from airborne noise inside the space. Windows are the transparent part of the façade, and to improve their thermal behaviour and control solar radiation, they are often fitted with a series of external and internal protections such as shutters, slats and blinds.This work contains a summary of studies carried out using field measurements of airborne sound insulation on façades in rooms, in application of the standard UNE-EN ISO 140-5:1999. In all the rooms the windows were fitted with shutter boxes and rolling shutters, and the acoustic tests were made with the shutter in two positions (extended and fully retracted). The results were analysed considering the window opening system (openable or sliding) and the type of glass pane (monolithic or insulating glass unit, IGU). In the case of sliding windows, the airborne sound insulation of façades is greater when the shutter is extended than when it is retracted, and this should be taken into account when applying the aforementioned standard.

On the uncertainty of building acoustic measurements – Case study of a cross-laminated timber construction

If variations and uncertainty in building acoustic measurements can be controlled, construction costs can potentially be reduced since the building will not have to be acoustically over-designed. Field measurements of impact and airborne sound insulation were carried out for an industrially prefabricated cross-laminated timber (CLT) system of plate elements. The results from 18 rooms, forming three groups with respect to size, were compared to a similar study dealing with a prefabricated Volume Based Building (VBB) system. Large variations were found at frequencies below 100Hz which is crucial for the low frequency adaptation terms connected to the weighted sound insulation indices. The measurement uncertainty was investigated by analysing the repeatability, measurement direction and the time dependence of the sound source. The variations due to the measurement procedure were found to be small compared to the total variations. It was also indicated that the variations in sound insulation are smaller with a prefabricated system compared to on-site production, since less work is required at the building site.

A ten year evaluation of the sound insulation of a volume based lightweight construction system

Since the middle of the '90s, Lindbäcks Bygg, a company in the North of Sweden has developed a lightweight timber construction system with industrially prefabricated room volumes. During these years, a lot of acoustic measurements have been performed. This information constitutes a valuable body of knowledge for future development of the system. However, the measurements have been performed by many different actors and are thus documented in many different ways, which means that it is difficult to get an overview. The aim of this project is to categorise all measurements of impact and airborne sound insulation that have been made on the volume system during the last ten years and to acoustically evaluate the significant constructional changes that have been implemented. A method to document previous and future measurements and link them to constructional parameters will be presented.

Influence of loudspeaker directivity and measurement geometry on direct acoustic levels over façades for acoustic insulation tests with the International Standard ISO 140-5

The International Standard ISO 140-5 on field measurements of airborne sound insulation of façades establishes that the directivity of the measurement loudspeaker should be such that the variation in the local direct sound pressure level (ΔSPL) on the sample is ΔSPL < 5 dB (or ΔSPL < 10 dB for large façades). This condition is usually not very easy to accomplish nor is it easy to verify whether the loudspeaker produces such a uniform level. Direct sound pressure levels on the ISO standard façade essentially depend on the distance and directivity of the loudspeaker used. This paper presents a comprehensive analysis of the test geometry for measuring sound insulation and explains how the loudspeaker directivity, combined with distance, affects the acoustic level distribution on the façade. The first sections of the paper are focused on analysing the measurement geometry and its influence on the direct acoustic level variations on the façade. The most favourable and least favourable positions to minimise these direct acoustic level differences are found, and the angles covered by the façade in the reference system of the loudspeaker are also determined. Then, the maximum dimensions of the façade that meet the conditions of the ISO 140-5 standard are obtained for the ideal omnidirectional sound source and the piston radiating in an infinite baffle, which is chosen as the typical radiation pattern for loudspeakers. Finally, a complete study of the behaviour of different loudspeaker radiation models (such as those usually utilised in the ISO 140-5 measurements) is performed, comparing their radiation maps on the façade for searching their maximum dimensions and the most appropriate radiation configurations.

Factors and Countermeasures Impacting Sound Insulation Performance of Light Steel Structure House Wall

The sound insulation performance of Light steel structure wall directly affects the quality of housing and people’s feeling. A theoretical analysis of the wall of light steel structure residential sound insulation performance is done, and some solutions in poor lightweight wall sound insulation measures is proposed.

Indirect measurement of acoustic power into a small room at low frequencies

An essential step towards improving sound insulation is a reliable means of quantifying the performance. However, for various reasons sound insulation measurements at low frequencies are associated with relatively high uncertainty and wide variance values. The objective of this research is to develop a method of sound insulation measurement which complements the standard ISO 140 measurement methods by providing improved accuracy at low frequencies. In this paper part of the problem is considered, namely the measurement of power radiated into the receiver room. The ‘peak envelope method’ is based on mode theory and the measurement employs a pair of microphones in the receiver room and a calibrated volume velocity source. No reverberation time measurements are required. The theory is outlined and computer simulations and trial measurements are carried out in order to validate the theory. Good agreement in numerical and experimental validation is demonstrated. We conclude that the peak envelope method is suitable for the measurement of radiated sound power at modal frequencies where ISO 140 methods are poorly adapted. In order to obtain transmission loss, a measure of incident power in the source room will also be required, which will be the subject of future works.

Acoustic failure analysis of windows in buildings

Poor acoustic insulation of building façades is largely influenced by the component assembly of the window and by the installation of the window in the wall. For the first, a poor gasket design and poor gasket installation during the window assembly will usually lead to whistle noises inside the rooms, especially next to busy roads. For the latter, the choice and installation of obturating materials in the cavity between the window and the wall may lead to a decrease in acoustic insulation in a wider range of frequencies. Consequently, the objectives of this investigation are to evaluate different methods to detect acoustical failures in openable windows in walls, and to present an efficient approach to optimise the sound insulation of a façade. By means of experimental measurements on a standard openable window, two different and complimentary approaches are compared to evaluate the acoustical quality and failures of the gaskets and the final setup of the window. More specifically, the first type of measurement is based on a standard sound insulation measurement of the façade according to ISO 140-5, and the second consists of ultrasonic measurements. The acoustic impact of the cavity between the window and the wall is evaluated in the laboratory according to ISO 140-3. For this research two different and most common materials are used to obturate the gap: polyurethane foam and mineral wool. The impact of these different types of materials is evaluated against different types of glazing. On the one hand side, standard sound insulation measurements enable to evaluate the quantitative impact of different parameters governing acoustical failures, such as discontinuity, incorrect placement and wrong selection of both gaskets and obturating material. On the other hand, ultrasonic measurements enable a quick qualitative assessment that is very efficient to determine the exact position of the acoustic leaks in the façade. Finally, a combined use of standard and ultrasonic measurements is proposed to deliver an efficient approach to detect acoustical failures of windows. The ultrasonic approach is a quick and cost-effective way to instantly track workmanship deficiencies of a window on site, whereas the standard measurements are more time consuming but needed to guarantee the performance of a building element.

Evaluation of air noise insulation of enclosing structures in extended frequency range

The airborne sound insulation measurement results and conclusions in a wider frequency range are described, else the influence of sample dimensions on results of measurements are shown.

Interference effects in field measurements of airborne sound insulation of building facades

The limits of the procedure for the measurement of the sound insulation of building facades represent the main subject of this paper.To calculate the facade insulation, standard ISO 140-5 requires that the difference between outdoor and indoor sound pressure levels is determined. However, the measurement of outdoor pressure levels presents several critical challenges, not fully considered in the standard. In fact, the placement of an external source and receiver according to ISO 140-5 is flexible to permit adapting the measurement configuration to specific building characteristics. Unfortunately, according to the relative external source and receiver positions, destructive interferences among waves may occur in different frequency bands. Comparisons between different source-receiver combinations are hence investigated theoretically, before being compared with field measurements. The paper investigates circumstances which might lead to destructive interferences in the external final sound field. The increasing attention of reproducibility in building acoustics suggests an investigation of possible measurement errors that may occur. The influence of interference effects on the single number rating of the sound insulation is finally given. © 2011 Institute of Noise Control Engineering.

Sound Insulation Descriptors in Europe—Special Rules Complicate Harmonization within Lightweight Industry

Many European countries have a sound classification standard connected to the building regulations in order to specify minimum requirements. The various national standards have a lot of similarities, however the acoustic descriptors differ more than what is obvious by a quick comparison of current classification standards. The different descriptors in each country are to some extent a heritage from the past, successively adapted to the building industry in each country and their certain traditions in building technique. The descriptors and the requirements are necessarily not based on subjective experience. Furthermore, to fulfil national interests and to fit to new design trends of housing units etc, the descriptors involve small local adaptations to each country. These local adaptations are not easy to find unless the standards are read carefully. This causes problem since the building industry is not restricted to national boundaries anymore. Many companies have activity in countries adjacent to each other and in future the probability for increased activity all across Europe and also outside Europe is to be expected, unless regulations restrict this development. Combining national special rules and some severe uncertainties in the measurement and evaluation procedures of sound insulation, the situation is more critical for lightweight structures. This is partly due to the fact that the development of building systems are made in one country, the production takes place in production plants, i.e. the production and the process are fitted to local regulations and are “standardized”. The standardized process is fast and dry but also needed due to lack of prediction models. And once the light weight system and the system process are established in one country it is complicated and expensive to adapt them to other countries. In this paper an overview of special national rules in some European countries and major problems connected to lightweight construction are presented.

Sound Insulation of Dwellings at Low Frequencies

The paper gives a summary of some recent measurements of sound insulation of dwellings at low frequencies (8 – 200 Hz), and compares these data to results from earlier measurements and to selected data from the literature. Data are given for the expected minimum sound insulation of typical Danish dwellings at low frequencies.

Evaluation and Measurement of Sound Insulation, Floor Impact Sound and Room Noise

Evaluation and Measurement of Sound Insulation, Floor Impact Sound and Room Noise

The noise insulation properties of non-food-crop walling for schools and colleges: A case study

The use of sustainable materials in building design and renovation has been driven by government initiatives such as the Code for Sustainable Homes, BREEAM and other assessment techniques. This paper presents the results from in situ measurements of insulation against unwanted sound (noise) for a sustainable walling system that has much anecdotal commentary concerning its good sound-insulating qualities: straw bale walls. The case study building in which the measurements were conducted is the Genesis Centre, an educational facility in Somerset. Schools need to be acoustically effective buildings, as pupils and students need to concentrate to take part in the education process. Sound insulation measurements were undertaken according to ISO 140: 4 – 1998 and Approved Document E (ADE) procedure, or as close to these standards as possible given the ‘as built’ nature of the case study buildings. With due regard for the limitations that an in situ measurement case provides, the acoustical data collected from these tests suggests that it is possible for straw bale walls to achieve the minimum requirements of Part E with a range of values of 48–50 dB DnT,w+C tr . These results are also compared with guidelines related to acoustics in schools and robust details.