Measurement Of Airborne Sound Insulation Research Articles

Effect of reverberation chamber volume on result of qualification procedure for loudspeaker and loudspeaker positions for airborne sound insulation measurements

Measurement of sound insulation from airborne sound is carried out by determining the level of sound power radiated by the test item. In laboratory practice, this translates into measuring the sound level in the transmitting and receiving chambers and measuring the reverberation time in the receiving chamber. When performing these measurements, significant fluctuations in the sound level for low frequencies can be observed, which is related to the occurrence of standing waves inside the chambers. To ensure proper level averaging, as well as repeatability and reproducibility of measurements ISO 10140-5 describes a qualification procedure for sources and source positions. This article presents the effect of increasing the volume of the source chamber on the results of the qualification procedure for sources and source positions for floor airborne sound insulation measurements.

Study of Acoustic Prototypes Based on Plastic Cap Waste

This paper presents the initial prototypes of solutions designed using plastic caps, seeking acoustic applications for both airborne sound insulation and the acoustic conditioning of rooms. Plastic caps are a waste product from the packaging sector and they constitute a major waste problem, given that, if they are not attached to the packaging, they get lost during the recycling cycle and end up in landfill. Finding an application for this waste that can provide acoustic improvements is a sustainable alternative. This paper shows the results of airborne sound insulation measurements obtained in a scaled transmission chamber and sound absorption measurements obtained in a scaled reverberation chamber for different combinations of single and double plastic caps and combinations with thin sheets of sustainable materials, such as jute weaving, textile waste, hemp felt and cork board. Tests have shown that obtaining sound reduction index values of up to 20 dB is possible with plastic cap configurations, or even up to 30 dB is possible at some frequencies with combinations of caps and certain eco-materials. With regard to the sound absorption coefficient tests, close to unity absorption values have been achieved with the appropriate configuration at frequencies that can also be selected. The results indicate that these panels can be eco-solutions for airborne sound insulation as lightweight elements, or they can be used for the conditioning of rooms, tailoring the sound absorption maximums to the desired frequencies.

Effect of Diffusing Elements in a Reverberation Room on the Results of Airborne Sound Insulation Laboratory Measurements

The main problem in the measurement of airborne sound insulation is the measurement of the sound power radiated by the barrier, in practice performed by measuring the sound pressure level and the acoustic absorption in the receiving room. Large variations of the sound pressure level in a reverberation room indicate the presence of dominating strong standing waves, so that it becomes necessary to install diffusing elements. In ISO 10140, the limits have been defined in which the reverberation time at frequencies at and above 100 Hz should be included. Sometimes, however, in the case of rooms with a large volume, obtaining the required parameters is difficult and sometimes even impossible. It should then be checked whether the measured sound insulation depends on the reverberation time. The paper presents the results of sound insulation measurements at various reverberation time lengths in subsequent stages of diffusing elements installation in the receiving room. An analysis of diffusing materials amount and arrangement influence on the uniformity of the sound pressure level distribution and reverberation time in the room as well as the value of the measured sound insulation was carried out. Uncertainty of sound insulation measurement with partial uncertainties was adopted as a criterion supporting the assessment of the obtained results.

Measurement of airborne sound insulation of building components by near-field acoustic holography

Taking the architectural acoustic design of a stadium and gymnasium in a sports center as an example, the acoustic parameters of large stadiums under different working conditions were explored. In order to improve the reliability of acoustic design of large stadiums, the acoustical environment of stadiums is simulated and matched with the design standard value by using the sound absorbing materials arranged in limited positions.

Validation of a 1:8 Scale Measurement Stand for Testing Airborne Sound Insulation.

This paper contains a detailed description of the design and validation of a measurement stand for testing the airborne sound insulation of specimens made at a small scale. The stand is comprised of two coupled reverberation rooms in which the geometry represents the full-size reverberation rooms used at the AGH University of Science and Technology at a 1:8 scale. The paper proves that both the scaled measurement stand and the testing methodology conform to the ISO 10140 standards, and that the obtained measurement uncertainty does not exceed the maximum values specified in ISO 12999-1. Moreover, the calculated uncertainty of measurements obtained for the 1:8 scale stand is comparable with the typical uncertainty given in ISO 12999-1 and the uncertainty obtained on the full-scale measurement stand. In connection with the above, the authors have proved that by using the scaled-down measurement stands, one can obtain reliable and repeatable results of measurements of airborne sound insulation.

Assessment of the low-frequency procedure in the field measurements of impact sound insulation between dwellings

In 2015, the new standard ISO 16283–2 for field measurements of impact sound insulation introduced a low-frequency procedure (LF-procedure) for measuring impact sound pressure levels and reverberation times at 1/3-octave bands below 100 Hz. The LF-procedure is followed when the volume of the receiving room is smaller than 25 m3. The LF-procedure is based on studies concerning field measurements of airborne sound insulation. Its aim is to improve measurement uncertainty of low-frequency sound insulation measurements. The procedure has not been assessed for use with impact sound insulation measurements. The objective of this study was to assess the standardized LF-procedure in the field measurements of impact sound insulation. The results show that the measurement uncertainty is improved. However, the impact sound pressure levels raise 4 dB on average. The values of L′n,w + CI,50-2500 and L′nT,w + CI,50-2500 also increase from 2 dB to 7 dB in most cases.

IMPLEMENTATION OF LABORATORY MEASUREMENT OF AIRBORNE SOUND INSULATION BASED ON ISO AND ASTM STANDARDS IN NATIONAL STANDARDIZATION AGENCY OF INDONESIA (BSN)

<p>The implementation of laboratory measurement of airborne sound insulation based on ISO and ASTM standards was carried out at SNSU BSN. The aim of this work to realize the measurement of airborne sound insulation for several sample tests, where the procedure of the test is performed according to the updated standard ISO 10140 and ASTM E90. Besides, the single number rating also is determined based on ISO 717-1 and ASTM E413. This measurement has been conducted in the two reverberation rooms using pressure method consist of measuring the sound pressure level, measuring the reverberation time, obtaining the sound reduction index (R) or sound transmission loss (STL), and determination of a single-number ratings of the samples test. From the results, some parameter requirements such as the frequency range and the rounding procedure of R or STL influence the measurement result slightly. Subsequently, the significant difference is obtained for the determination of single number rating in the shifting procedure of the reference curve.</p>

UNCERTAINTY ANALYSIS OF LABORATORY MEASUREMENT OF AIRBORNE SOUND INSULATION

The evaluation and analysis of the uncertainty of laboratory measurement of airborne sound insulation have been carried out by Research Group for Acoustics and Vibration – National Standardization Agency of Indonesia (BSN). The aims of this work are to evaluate and analyze the uncertainty measurement of airborne sound insulation by pressure method, where it is focused only for the determination of sound transmission loss (STL) as a major product of this measurement according to ASTM, and guide to the expressions of Uncertainty in Measurement (GUM) provided by JCGM. The supplied parameter of uncertainty budgets includes measurement of sound pressure level (SPL) in a source room (L1), and measurement of some parameters in a receiver room such as SPL (L2), reverberation time (RT60), background noise (B), test opening area (S), and volume of receiver room (V). From the result of the case study, the source of uncertainty that has a top contribution for obtaining expanded uncertainty is considered as the repeated measurement of the measured parameter such as L1, L2, and RT60 at the frequency range 250 Hz – 315 Hz. Meanwhile, the standard uncertainty that provided by the calibration certificate also contributes to the final result, where it is supplied by an acoustic calibrator and sound analyzer, respectively. Furthermore, the sources obtained from the readability parameter has a slight effect on this whole result. Therefore, the maximum and minimum value of expanded uncertainty is determined that their values are 0.70 dB and 0.43 dB for the frequency of 315 Hz and 1600 Hz, respectively.

Measurement of Airborne Sound Insulation of Modular Construction Methods

Measurement of Airborne Sound Insulation of Modular Construction Methods

Remarks on the definition of airborne sound insulation and consequences for uncertainties

Airborne sound insulation is explicitly defined as the ratio between incident and transmitted sound power. Since sound power cannot be measured directly, field quantities like sound pressure are measured to derive the desired sound power. The relation between sound pressure and sound power depends on the nature of the sound field, i.e., to which extent it is a diffuse sound field. This is the main reason why it is impossible to derive an analytic equation for the measurement uncertainty of a sound power and thus of a sound insulation. The current practice is to define standardized test facilities for the measurement of airborne sound insulation. The uncertainty of measured sound insulations is then approximated by the standard deviation of reproducibility determined by interlaboratory tests. This is equivalent to changing the definition of airborne sound insulation. It is no longer the sound power ratio but the mean value of the sound insulation measured in very many or all thinkable laboratories meeting the required specifications. Thus, laboratory specifications become part of the definition of airborne sound insulation. The contribution highlights the background of the different definitions and shows consequences for the uncertainty of airborne sound insulation.

On the use of finite-element methods to minimize uncertainties in airborne sound insulation measurements in the low frequency range

Measuring airborne sound insulation at low frequencies (below 100 Hz) may be very challenging. In fact, to cope with this problem ISO 16283-1:2014 also included a dedicated procedure for smaller rooms, having a volume below 25 m3. However, even in significantly larger rooms, large spatial variations of sound pressure levels may appear, resulting in a measure which is largely affected by the choice of the measurement positions. Considering that simple rooms may be easily modeled using finite-elements tools, it may be advantageous to carry out a preliminary numerical analysis of the spatial distribution of the one-third-octave levels, so to minimize measurement uncertainty. The room space is first subdivided by means of a 3D grid where sound pressure levels are determined using a finite element model. Then, the receiver positions compatible with standard requirements are identified, and, finally, a statistical analysis of the measurement uncertainties is carried out. Comparisons between simulations and measurements are finally illustrated.

The Use of Sound Absorbing Shading Systems for the Attenuation of Noise on Building Façades. An Experimental Investigation

The problem of solar irradiation in building façades with large windows is often solved with the use of external shading devices, such as brise-soleil systems, but their potential acoustic effects on building façades are usually neglected. The purpose of this work is a preliminary consideration of the acoustic behaviour of brise-soleil systems and, furthermore, the evaluation of the possibility to improve their performances, in terms of Sound Pressure Level (SPL) abatement over glass surfaces. The paper reports the results of a study on two portions of the same office building, with shading devices installed in front of large windows. Both airborne sound insulation measurements and SPL measurements over the glass surfaces of the windows were carried out to compare different situations, with or without louvers, and with sound absorbing experimental louvers as well. Results show that the louvers' presence can produce an increase in the SPL over the glass surface as a consequence of the reflection of the sound. Results further show that sound absorbing louvers improve the noise protection of the system, in terms of the SPL reduction, over glass surfaces, cancelling out the negative effect of the standard shading devices.

Justification of standardized level differences in rating of airborne sound insulation between dwellings

It has long been recognized that single-number quantities R′w, DnT,w or Dn,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 0.5s 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 DnT,w would lead to higher transmitted sound levels of living sounds in larger rooms, but this was not detected. The use of DnT,w makes rooms of different volumes equal in regard to required sound insulation between them. It is thus justified to replace R′w with DnT,w as the SNQ for rating the airborne sound insulation. Widening the frequency range down to 50Hz or up to 5000Hz did not give noteworthy improvement in the correlation.

State of field measurement of facade sound insulation in buildings: evaluation of proficiency testing data according to ISO 140-5:1998

The ISO 140-5:1998 standard specifies the testing methods to evaluate the sound insulation in buildings and building elements for facades. Three rounds of a proficiency testing scheme for airborne sound insulation measurements have been performed according to the methods specified in the standard for a whole facade by using an external loudspeaker as the noise source. The adequacy of the intercomparison is guaranteed by means of the assessment of global precision criteria in compliance with the scope stipulated by the normative references in order to determine the reproducibility limits in a regulated measurement method. To evaluate the participant performance, the corresponding combined scores as composite indexes are calculated, so if this assessment is performed along a certain number of rounds, it will remark the participants that show an overall satisfactory performance by monitoring their achievement over time. Therefore, in order to establish a reference value in terms of precision level, an approach based on the development of a collaborative test in controlled conditions is proposed. The goal is to provide reliable and updated criteria for the evaluation of repeatability and reproducibility limits in this field, particularly in those scopes in which nowadays there is no normative reference or this is very poor. Furthermore, these prescribed values of precision should be verified regularly, as well as the definition of practical conditions of application.

Uncertainty determination of in situ airborne sound insulation measurements

In building acoustics the measurement uncertainty of sound insulation measurements is traditionally either not reported or reported as stated in the corresponding standard ISO 12999–1:2014. Determination and application of measurement uncertainties in building acoustics—Part 1: Sound insulation (former ISO 140-2). An alternative procedure is presented in this paper, aiming at evaluating the need of performing individual uncertainty calculations and the effect of extending the frequency range used to calculate sound insulation single number quantities. A large set of in situ airborne sound insulation measurements is investigated following the ISO Guide to the Expression of Uncertainty in Measurement (GUM) both for DnT 1/3 octave bands values and for single number rating DnTA. Two alternative assessment frequency ranges (50/100–5000Hz) have been considered. The paper describes a methodology for uncertainty determination to emphasize that it is possible to determine such individual uncertainties following the ISO GUM approach to a certain extent and that each individual measurement needs a corresponding measurement uncertainty calculation. In addition, the results show that if the assessment frequency range is extended below 100Hz, the uncertainty of the single number quantity is increased.

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.

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.

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.

On the Method for Laboratory Measurement of Airborne Sound Insulation of Small Building Elements

On the Method for Laboratory Measurement of Airborne Sound Insulation of Small Building Elements

Uncertainty evaluation in field measurements of airborne sound insulation

The Brazilian Committee of Civil Engineering presented a set of standards concerning the evaluation of the performance of several topics for buildings up to five floors. The acoustic performance is one of them. The standards are in approval process and measurements in real buildings will be necessary. Different professionals using different equipment will emit certificates establishing which levels of insulation a certain flat provides and its uncertainties. The expanded measurement uncertainty can provide the basis to compare different measurement results for a same building. The international Guide to the Expression of Uncertainty in Measurement, the ISO GUM, is the document that specifies how to determine and evaluate the uncertainty of a measurement result. The standards concerning sound insulation measurements are ISO 140 and ISO 18233. Uncertainty estimates are available only for the classical technique described in ISO 140, based in repeatability and reproducibility tests performed in laboratories. Field measurements present some characteristics that can contaminate the results, as time variance. Several independent measurements were carried out in a one flat building using ISO 18233 specifications and the ISO GUM was applied to obtain the uncertainty for measurement results of airborne sound insulation between rooms in situ.