Sound Transmission In Buildings Research Articles

Vibration reduction index improvement by adding resilient strips: influence of junction properties

Resilient strips can be used to decrease the structural transmission in junctions and thus limit the flanking sound transmission in buildings. In the standard ISO 12354-1, the efficiency of a resilient strip is characterized by the vibration reduction index improvement. To evaluate the vibration reduction improvement, a standardized measurement method is needed. However, the vibration reduction improvement is not an intrinsic material parameter of the resilient strip and can depend on the mounting conditions and junction geometry. In this paper, the vibration reduction index improvement is evaluated by means of numerical simulations carried out with a statistical model for junctions with resilient strips. The model was first validated by laboratory measurements. While the influence of the junction type (L, T or X) and transmission path (straight on or around the corner) is limited, the influence of the plate properties (mass and bending stiffness) cannot be neglected, with differences in vibration reduction improvement of up to 20 dB.

Insertion loss of pipe clamps: Quantity for prediction or manufacturer's advertising?

The noise emitted by water conveying pipes as part of sanitary installations is, in most cases, dominated by structure-borne sound transmission. The water flowing through the pipe causes a vibration of the pipe system that is transmitted to the installation wall through pipe clamps. A common mitigation measure is an elastic inlay inside the pipe clamps. Some manufacturers of these clamps advertise the insertion losses determined by non-standardized tests. Recent studies show a high dependency of the insertion loss on the mounting conditions, e.g. how tight are pipes fastened in the clamp. This contribution aims to answer the question of whether and how the mounting condition affects the insertion loss of the pipe clamps and thus how representative the specified values can be for the building situation. The investigations are carried out in-situ on the reception plate and in a building like test stand with an excitation by flowing water as well as with impact hammer excitation. This study is part of a research project with the overall aim to provide source data for the prediction of the sound transmission in buildings using EN 12354-5.

Acoustic Properties of Innovative Concretes: A Review.

Concrete is the most common building material; therefore, when designing structures, it is obligatory to consider all structural parameters and design characteristics such as acoustic properties. In particular, this is to ensure comfortable living conditions for people in residential premises, including acoustic comfort. Different types of concrete behave differently as a sound conductor; especially dense mixtures are superior sound reflectors, and light ones are sound absorbers. It is found that the level of sound reflection in modified concrete is highly dependent on the type of aggregates, size and distribution of pores, and changes in concrete mix design constituents. The sound absorption of acoustic insulation concrete (AIC) can be improved by forming open pores in concrete matrices by either using a porous aggregate or foam agent. To this end, this article reviews the noise and sound transmission in buildings, types of acoustic insulating materials, and the AIC properties. This literature study also provides a critical review on the type of concretes, the acoustic insulation of buildings and their components, the assessment of sound insulation of structures, as well as synopsizes the research development trends to generate comprehensive insights into the potential applications of AIC as applicable material to mitigate noise pollution for increase productivity, health, and well-being.

A review of ASTM International standards relating to impact sound transmission in buildings

Impact sound transmission in buildings is an important issue, especially in today's multifamily marketplace where the trend to replace carpet with hard surface flooring is becoming more popular every year. This presentation will discuss the many changes that have been made over the years to the laboratory and field test methods for evaluating impact noise in buildings, including new standards under development.

Virtual reality meets architectural acoustics

Computer programs for simulation and auralization of sound fields in rooms and of sound transmission in buildings became standard tools for architectural design and consulting. Another field of rapid progress is Virtual Reality—the combination of real-time signal processing with user interaction and multimodal human-machine interfaces. In this contribution, the development of simulation tools in architectural acoustics and further work aiming at real-time Acoustic Virtual Reality systems are reviewed and discussed with emphasis on the challenges and interdisciplinary solutions involving architectural acoustics as well as signal processing and psychoacoustics.

Non-standard uses of the mechanical tapping machine in field measurements

The mechanical tapping machine creates a continuous series of floor impacts which generate a steady-state sound field when measured indoors. Because each individual hammer has the same weight and free-falls from the same distance, the machine creates a calibrated and steady impulsive force into the floor structure. This presentation will illustrate potential future test methods for assessing sound transmission in buildings with examples to evaluate structure-borne sound transmission into structurally isolated anechoic and reverberation rooms.

Update on the change in sound insulation requirements in Canada

In the 2015 edition of the National Building Code of Canada (2015 NBCC, published in January 2016), sound insulation requirements between dwelling units are given in terms of Apparent Sound Transmission Class (ASTC). This is a significant change from the requirements in previous editions of the NBCC which were given in terms of Sound Transmission Class (STC). While the STC rating only accounts for sound transmission through the separating assembly, the ASTC rating also takes into account structural flanking transmission via adjoining building elements. An overview of the change in requirements and of NRC activities to support the code change was given at the ASA meeting in Jacksonville (November 2015). This presentation will provide an update on the implementation of the code change since it came into effect in federal regulations in early 2016. Tools and guidelines provided by the NRC such as Research Report RR-331, “Guide to Calculating Airborne Sound Transmission in Buildings” and the revised version of soundPATHS, NRC’s web application to calculate ASTC ratings, will be presented.

Flanking sound transmission in connected panels of cross-laminated-timber at low frequencies

The sound transmission between adjacent rooms can be dominated by the structure-borne sound transmission in the flanking walls. A wall can be defined as a subsystem of the overall system based on two coupled rooms. These subsystems show local modes, if they are not connected to each other. In contrast, connected subsystems result in global modes showing a high response of both subsystems, if the comparable local modes have similar eigenfrequencies. The flanking sound transmission especially at low frequencies is reduced, if a generation of such global modes can be suppressed. As a consequence, the flanking sound transmission in buildings can be mitigated significantly using a proper design of the walls (geometry, material, etc.). The principles and the impact of this effect are studied in this paper using numerical models based on the finite element method. Selected constructions are implemented in real size 2D- and 3D-models of two adjacent rooms. Panels of cross-laminated-timber are used because the variable composition of the single layers of a panel allows an extensive variation of the vibration response of the single walls. The results confirm the applicability of the described effect for common practical situations.

The use of damping to reduce the contribution of flanking paths to sound transmission in buildings

The importance of flanking paths to sound transmission in buildings has been studied recently. Damping treatments make it possible to increase the internal losses in structures and provide an opportunity to enhance the attenuation of long transmission paths. A number of numerical comparisons have been made to demonstrate the effectiveness of a global increase in structural damping of nine different physical systems using both bending only and three-wave models. Statistical energy analysis (SEA) has been adopted as the analytical framework. The results show that, by applying a damping treatment, the contribution of flanking paths to sound transmission can be reduced and sound insulation improved.

Finite-difference time-domain analysis of the vibration characteristics of a beam-plate structure using a dimension-reduced model

In order to accurately predict the vibration characteristics of structure-borne sound transmission in buildings, wave-based numerical methods are effective from the viewpoint of the modeling accuracy of the physical mechanism and the detailed geometries of the simulated field. However, because of the performance of current PCs, the prediction of real-scale problems remains difficult. In order to address such problems, we herein propose a vibration simulation method for a beam-plate structure using a dimension-reduced modeling method. The target structure is modeled as a composite structure consisting of two-dimensional plate elements and one-dimensional beam elements, which are coupled based on the implicit finite-difference approximation scheme. By applying such a low-dimensional element, a faster simulation that requires less memory, as compared with a three-dimensional discretization scheme, is made available. Good agreement between the measured and simulated results for the vibration characteristics of acrylic beam-plate models indicates the validity of the proposed method.

Towards a prediction of the sound transmission from lightweight stairs

The sound transmission from lightweight stairs which are connected to separating walls often gives rise for complaints. One reason for this is that at present there is no prediction method available. Treating the stair as an active component in a similar manner like vibrating machines stairs can be characterised as structure‐borne sound sources. The source data then can be used to predict the sound transmission in buildings using parts of EN 12354. Following this approach investigations on a timber stair have been carried out in a staircase test facility. Based on a full characterisation by contact free velocity and mobility and in‐situ measurement using an indirect method, more practical methods like the reception plate method and a characterisation based on a reference power calibration are investigated. The source data obtained was used to predict the sound transmission in buildings.

Acoustical proprieties of light brick walls and its effects on flanking transmission

Light brick walls 8-10 cm thick are typical structures frequently used in Italian building constructions as a internal partitions between dwellings and as internal layer of double façade walls. Due to low surface mass and rigid connection to other horizontal and vertical structures, light brick walls are often responsible of high flanking transmission. The simplest acoustic modeling of this structure for the evaluation of sound transmission in buildings, is the approach proposed by the EN 12354 standards, where the brick wall can be considered as a homogeneous structure and main acoustic parameters required are the sound reduction index and the vibration reduction index Kij. The aim of this paper is to analyse results of physical and acoustical properties (sound reduction index, structural reverberation time, radiation efficiency) of a typical 8 cm thick brick wall measured in laboratory testing facility, used as a partition in different test configuration: single layer wall, double brick layer wall with internal thermal layer and as a component of lateral wall, where the Kij index flanking transmission were also evaluated. Experimental results are then compared with theoretical values in order to analyse difference with homogeneous structures.

Effects of Air-Layer Subdivision: A New Method of Improving Sound Insulation

In the impact of floors, sound transmission through walls, and structure-borne sound transmission in buildings, there is a possibility of improving the insulation by restricting the air particle motion at the interface of the vibrating surface and the air. One of the practical ways for realizing this condition is by subdividing the air layer at the interface in the direction parallel to the radiating surface. This novel method for noise control has an attractive simplicity and a real practical benefit. In this paper, the mechanism, causing this effect, is discussed using analytical models of acoustic radiation and sound transmission. As a result of this investigation, it is seen that the effect of this method is characterized by reduction of acoustic radiation at low frequencies near and below the critical frequency of coincidence. The method is validated experimentally.

Isolation of Buildings from Ground-Borne Noise Using a Sand Stratum

The effect of an elastic stratum in reducing ground-borne sound transmission in buildings to be built above railway tunnels is investigated, by considering a sand layer between the bedrock and load bearing elements of the building. It is assumed that the initial vibrational energy that propagates from the foundation is in the form of quasi-longitudinal waves. The complete model as presented by the author in a previous paper is considered. Calculated results are compared with previous results for a typical building and it is shown that a sand layer can considerably reduce upward sound transmission in the building. The results of a parametric study to investigate the influence of the type of load-bearing elements and the thickness of the layer, on transmission of structure-borne sound in the building, are presented.

The contribution of long flanking paths to sound transmission in buildings

Recent developments in calculation models for sound transmission in buildings have concentrated on the direct path and the flanking paths that cross only one structural joint. However, in real buildings there will be many other paths involving transmission across more than 1 structural joint and although these paths individually will be relatively unimportant their overall contribution can be significant. A number of numerical case studies were undertaken and it is shown that for many cases these longer paths are together more important than the first order flanking paths which in turn are often more important than the direct path. This suggests that although including first order flanking paths into a mathematical model will improve the agreement between measured and predicted data large errors may still occur if other parts of the building are not included.

Structure-borne transmission in lightweight buildings

The move away from mass as a means of reducing sound transmission in buildings has led to the development of lightweight buildings. High levels of sound insulation are achieved by introducing discontinuities while retaining structural integrity. This paper will examine structure-borne sound transmission in lightweight framed buildings. For sound transmission through a wall or floor it is the coupling between the frame and the lightweight panels which must be considered. The coupling can be classified as either a line connection or a point connection. Each of these cases will be examined and the theories for sound transmission compared with experimental results. Flanking transmission must also be considered and models for the coupling between the structural elements will also be examined. These models are different from traditional buildings as many of the elements behave as beams rather than as plates. The structure is therefore a collection of beams and plates rather than just plates. Some of the transmission paths for transmission between adjacent rooms will be examined both for the case where all walls and floors are lightweight constructions and for the case where there is a mixed construction with traditional walls but lightweight floors.

The use of semianalytical calculation models to verify SEA predictions of flanking transmission in building structures

The prediction of structure-borne sound transmission between coupled plates represents a key aspect when studying sound transmission in buildings, since vibrational energy flow between walls and floors leads to the existence of flanking paths. The resulting flanking transmission can be assessed theoretically using statistical energy analysis (SEA). In this method, the coupling between plates is usually estimated based on the wave approach for the corresponding semi-infinite plates. For a specific type of junction, one might consider verifying the predictive performance of SEA experimentally on an isolated plate junction. However, possible discrepancies between measured and predicted data can result either from the failure of the calculation model for the semi-infinite plates, or by the violation of the basic SEA assumptions. In this paper, a semianalytical calculation model based on a modal summation approach for finite-sized plates is proposed to determine the source of the prediction error. For this purpose, calculations are performed for two ensembles of similar corner junctions with randomly distributed dimensions. The analysis emphasizes the influence of the model overlap factor on the accuracy of SEA. [Research funded by the Flemish Institute for the promotion of Scientific Technological Research in Industry (IWT).]

The consequences of lightweight buildings on sound transmission

Changes in building practise have led to an increased use of lightweight components in modem buildings. Lightweight walls and floors do not rely on mass to prevent sound transmission but on the way in which the various components with different material properties are combined. This requires a knowledge of both the materials used and the details of construction. The traditional approach to design is to compare the proposed construction with measured data from similar systems. However, the possible range of lightweight designs makes this impractical. Theoretical models offer an alternative approach to design and are becoming increasingly important for sound transmission in buildings.

Sound transmission in buildings with elastic layers at joints

The influence of elastic layers (ELs) at junctions between walls and floor slabs on airborne and structure-borne sound transmission in buildings is investigated. For this aim, we carried out measurements on scale models with ELs at the joints. The results were compared with the predictions of the statistical energy analysis model. This model included the theoretically calculated transmission coefficients for junctions between elastically coupled plates. As a practical application, we analysed the performance of ELs in a model for a real building structure and for various positions of ELs. The work showed that the benefits of the use of ELs depend on the specific situation: the effect can be either positive or negative. In fact, the global effect of ELs is only a change in the distribution of the total energy. If less energy is transmitted into one direction, more energy will be transmitted into the other one.

Sound transmission by coupled structures: Application to flanking transmission in buildings

In the paper a new formulation for sound transmission by coupled structures with special application to flanking transmission is presented. As distinct from other approaches in which the couplings are considered to be similar, this method treats each type of coupling specifically: the mechanical/mechanical coupling is rigorously treated; the mechanical/acoustic coupling is considered to be weak, this hypothesis being generally admissible when air is the acoustic medium fluid. The formulation proceeds from the general to the specific; in this way, it is easier to measure the effect of the hypothesis introduced. The theoretical procedure for defining the transmissions leads to an experimental method in which measured data of the energy and spectral densities of the forces is used. The application of this method to the case of sound transmission in buildings was carried out to serve as an example. The proportions of the energy transmitted by the dividing wall and the flanking walls were calculated to diagnose the situation and thereby to improve the insulation between the rooms. An interactive computer program is being proposed and will be available to users.