Sound Reduction Index Values Research Articles

Retrofitting masonry and cavity brick façades for different noise zones using laboratory measurements

Façade airborne sound insulation is crucial for protection of indoor environment from environmental noise. In Turkey, sound insulation in new buildings is bound by law, but 6 million pre-1980 dwellings with thin brick walls and single-glazed windows used in highly transparent façades should be retrofitted. In this study, sound reduction index of masonry and cavity exterior walls which consist of brick, mortar, gypsum board and mineral wool and of common window types is measured in sound insulation test rooms. The study compares and evaluates the effects of plaster, brick thickness, cavity depth, mineral wool thickness and mineral wool placement on sound reduction index values, using traditional materials and building techniques. Traditional brick wall façades and possible retrofitting of these façades are evaluated for sound insulation of bedrooms and living rooms in different noise zones, 55, 60, 65, 70 and 75 dBA, with various transparency ratios, 0%, 30%, 40%, 50% and 70%. The analysis shows that window types and single-layer walls are the deterministic factors in evaluating sound insulation in retrofitting projects and that it is not possible to provide proper aural comfort in high noise zones.

Theoretical Determination of Sound Reduction Index of Simple Walls on Various Material Bases

The contribution deals with a comparison of measured and calculated values of sound reduction index R (dB) and weighted sound reduction index Rw (dB) of simple walls from various materials. In this way it verifies the exactness of a modified calculation-graphic method according to Watters and an appropriateness of its application for simple walls from various materials with the focus on the aerated concrete walls.

Propiedades acústicas de los paneles de carrizo

Reed is a plant species very similar to common cane which is widespread all over the Earth. It is an ecological and sustainable material which is low-cost, aesthetically attractive, easy to obtain and install, and can be used in different construction systems. This work analyses the acoustic properties of reed panels from the point of view of sound absorption and sound insulation against airborne noise, according to the corresponding EN ISO standards. The experimental results obtained point to the conclusion that reed panels are suitable construction systems for controlling reverberant sound within a space, and that the sound reduction index values for different thicknesses of reed panels, or reed panels used in combination with wood particle boards, demonstrate the possibility of using them in construction as an element on the facades and roofs of buildings and for interior partitions.

Scale Model Investigation on the Influence of Boundary Conditions on the Airborne Sound Insulation of Lightweight Double Walls

Sound reduction index measurements were performed inside a 1:10 scale model of two adjoining rooms of a test facility in an acoustic laboratory, with the aim of investigating the influence of the boundary conditions on the acoustic performance of lightweight double walls. The model was built entirely of polymethyl methacrylate (PMMA). The specimen double walls were built using the same acrylic material. At first, measurements were performed on a single homogeneous panel, in order to check the reliability of the whole procedure and the repeatability of the measurements. A good correspondence was found between theoretically calculated values and measured values of the sound reduction index above the critical frequency. A second set of measurements was carried out on model double walls comprising two leaves, connected to each other only by a border frame running along the whole wall perimeter. It was found that the effect of the border frame is a reduction of the performance of the double wall, to under that of a single plate with the same total surface mass. A third set of measurements was carried out inserting vertical studs to connect the two leaves. It was found that the presence of the studs causes a general decrease of the sound reduction index values and a decomposition of the critical frequency. A fourth set of measurements was carried out on the same double wall using border frames made of different materials. The experimental results show that damped materials (wood, rubber) give a better performance than rigid materials (acrylic, aluminium).

An Investigation into the Reproducibility Values of the European Inter-Laboratory Test for Lightweight Walls

In an inter-laboratory test programme (ILT) for the measurement of airborne sound insulation of lightweight walls, reproducibility values of up to 12dB were obtained from the sound reduction index measured in 21 participating laboratories. These high reproducibility values were for a test structure composed of lightweight plasterboard panels, forming a double wall, mounted on separate metal ‘C’ channels. This paper presents possible reasons for the large reproducibility values for the double wall using experimental investigations and theoretical models using Statistical Energy Analysis (SEA). Whilst the sound reduction index(SRI) does take into account the different test wall areas and reverberation times of the respective laboratories involved, some factors which may influence the measured SRI values are not. It is suggested that the principle factor which may have effected the SRI values of this test programme for the double wall was the lining material of the test aperture in the various laboratories which can provide a flanking transmission path between both sides of the double wall. Other factors are discussed which may also play a contributory role in causing differences in the measured SRI values such as sill/reveal size, aspect ratio, panel-channel connections and workmanship.

Inter-Laboratory Test of Sound Insulation Measurements on Heavy Walls: Part I — Preliminary Test

The intention of sound reduction index (SRI) measurements in transmission suites is to obtain more reliable values of the specific test element's sound insulation properties. Unfortunately, these values are influenced by the mounting of the test element itself and the construction design of the test facility. Both the mounting of the test element and, in part, the design of the test facility can effect the damping of the test element. From previous studies a suggested solution has been to take into account the damping in terms of the test element's loss factor. By incorporation of the loss factor in SRI measurements, of heavy walls, it has been suggested that this could reduce the deviations in SRI values due to laboratory influences. To determine the variance of sound transmission measurements in test facilities for a heavy wall, an inter-laboratory test (ILT) was performed in twelve different institutes. This ILT study included the measurement of sound reduction index, velocity levels and damping. In this first part, of a two part paper, a review concerning the principle previous studies is given. Furthermore, decisions regarding the choice of the test element, principal measurements and participating laboratories are reported.

An Intercomparison of Laboratory Measurements of Airborne Sound Insulation of Lightweight Plasterboard Walls

This paper describes the results of the European Inter-Laboratory Test (ILT) program, conducted for the determination of repeatability and reproducibility values for the laboratory measurements of airborne sound insulation of walls. A total of 24 laboratories took part in this ILT, 21 belonging to the European Community. Two test structures were constructed; a double lightweight wall and a single lightweight wall, both built of plasterboard. The sound reduction index values were measured. The main result of the ILT was the significant difference obtained for the reproducibility value, R, for the double lightweight wall with values up to 12 dB at middle-high-frequencies. On the contrary, the reproducibility value for the single wall was very similar to the tentative values indicated in Annex A of ISO 140–2. Good agreement between laboratories was found for both structures in the computed repeatability values, r.

Predicting the sound reduction index of laminated glass

Vibration tests on small samples have been used to obtain the critical frequencies and loss factors of 7 mm, 9 mm and 11 mm laminated glass. The Sound Reduction Index (SRI) as a function of frequency has then been predicted using Sharp's method. The predictions have been compared with measured values of SRI obtained from reverberant room tests on 1·25 by 1·5 m windows. The predictions are good, particularly of the critical frequency and of R w . The measured SRI exceeds the mass law, possibly as a result of the relatively small window size in relation to the depth of the test aperture. The prediction method needs refining in the vicinity of the critical frequency.

Inter-laboratory comparisons of low-frequency sound transmission: I. Conventional and intensity measurements

Sound transmission through nominally identical steel plates was measured in two laboratories; NRC, Canada and PTB, Braunschweig in Germany. The two laboratories differ markedly in construction; one has rooms with volumes 65 and 250 m3 and the other volumes of 54 and 69 m3. The specimens measured 1.5×1.25 m and were mounted in window test frames that satisfied the recommendations of ISO 140. The measurement frequency range was extended to 50 Hz in each laboratory. As well as conventional 1/3-octave band measurements, sound reduction index was measured using sound intensity techniques. Measurements were made in both directions, that is, each room served in turn as the source room and then the receiving room. Similar behavior was seen in each laboratory; conventional measurements into the smaller room tended to give higher values of sound reduction index. When the mean values of sound reduction index for each laboratory for both directions of measurement are compared, agreement is good but there are still differences at low frequencies that need explanation. This paper presents the measured data. Possible reasons for the differences are discussed in the companion paper.