Impact Sound Transmission Research Articles

The Impact Guide: Adapting ISO 12354-2 for calculating impact sound transmission to the North American context

To support a potential introduction of an impact sound requirement into one of the next editions of the National Building Code of Canada, the National Research Council of Canada has initiated several research projects. For one of these projects, an industry-sponsored consortium has been formed with the goal of providing supporting documents and online tools to help building designers incorporate impact sound requirements into their work. The main guide document, following the model of research report RR-331 for airborne sound, provides guidance and explanations on how to calculate and combine direct and flanking sound transmission, in this case for impact sound. The guide uses the method given in ISO 12354-2, adapted to the relevant ASTM standards used in North America. This contribution provides an overview of the work to create the impact sound guide document, how the implementation of ISO 12354-2 is achieved using ASTM standards and presents several example calculations highlighting the need to consider flanking sound transmission for impact sound.

Energy harvesting and inter-floor impact noise control using an optimally tuned hybrid damping system

Impact-loaded floor structures radiate undesired sound waves into adjacent rooms, compromising the acoustic comfort. On the other hand, substantial structural vibrations caused by the impact loading offer a promising energy source for harvesting. Nevertheless, a systematic analytical or numerical investigation of simultaneous inter-floor impact sound transmission control and energy harvesting appears to be missing. Current study describes the conceptual development of a fully coupled 3D analytical model of a dual-functional double-plate floor structure optimized for hybrid regenerative control of inter-floor impact sound transmission. Leveraging multi-mode shunted piezoelectric and Electromagnetic Damper (EMD) energy transduction mechanisms, the model structure is composed of two PZT sandwich plates, which are interlinked through a Nonlinear Vibration Absorber (NVA)-based EMD. The finite Fourier cosine transform and standard normal mode approach are employed to treat the governing acousto-elastic equations. Non-dominated Sorting Genetic Algorithm II is applied to tune the system parameters along Pareto frontiers to target maximum pressure mitigation, maximum energy harvesting, or dual-objective optimization, which hires advantageous features from both configurations for an optimal trade-off between them. Simulations reveal that elasto-acoustic response suppression and energy extraction of the employed stand-alone PZT-based conversion mechanism can be remarkably improved with the adopted optimized hybrid PZT/NVA/EMD-equipped system.

The sound of sustainable structures: Acoustic considerations for mass timber

The use of mass timber in multi-family and commercial buildings poses a range of challenges for acoustic designers, due in part to its recent emergence as a structural technology and relative light weight compared to concrete. The spectral performance of mass timber assemblies differs from that of concrete and of lightweight double-panel systems, such as timber joist floors, even when comparing assemblies with the same single-number airborne and impact sound transmission ratings. Due to the inclusion of mass toppings and damping layers, mass timber floor designs may outperform lightweight double-panel systems at low frequencies, but they are often challenged at mid to high frequencies, resulting in a sound spectrum that differs from established “acoustically acceptable” benchmarks. This study presents initial findings from listening sessions conducted in the Arup SoundLab, as well as various design strategies to balance performance, cost, aesthetics, and sustainability.

Impact Sound Insulation of thermally insulated Balconies

With the increasing urban densification, balconies are gaining in popularity as they improve the living quality in homes. Thermal insulation between balconies and the building's façade is state of the art. In Germany the most popular balcony construction is a reinforced concrete balcony, separated from the building by a thermal insulation element (TIE), which is meant to reduce the thermal energy loss and thus ensure the sustainability of buildings. The impact sound transmission from balconies, however, is a problem that has not been addressed enough to date. The main goal of the project is to provide acoustic quantities, e.g., an impact sound reduction, for a TIE that can be used to compare the acoustical quality of products and to predict the impact sound pressure levels within the building using the standard EN ISO 12354-2. Experimental and numerical studies have been carried out on various ceiling-balcony mock-ups without and with TIEs e.g., by means of experimental modal analysis and finite element models. This paper will show the effect that various parameters have on the impact sound insulation. Additionally, the measurements on the test set-up will be compared to measurements on building sites.

Numerical and experimental investigation of the narrow-band impact sound insulation of layered floors

Measurement results of the impact sound insulation of (floating) floors are generally limited to one-third octave bands. As a consequence, detailed information on modal behavior and on the influence of the impact source, are largely lost due to band-integration. To this end, narrow-band measurements are performed on five different layered floors. Various tapping machine locations are considered and the results are averaged over several receiver positions for each tapping machine location in order to reduce the influence of the spatial distribution of the sound pressure in the receiver room. A new prediction model for impact sound transmission, termed the modal TMM, or mTMM, is used to interpret and investigate the measurement results. This prediction method includes a detailed source model and accounts for the finite dimensions of the layered floors. The measurement results of the layered floors clearly indicate the importance of considering all five impact hammer locations of the tapping machine to achieve a high prediction accuracy, especially at low frequencies. The influence of the impact source and the modal behavior of the floor can lead to high peaks in the radiated sound power level.

Evaluating Laboratory Measurements for Sound Insulation of Cross-Laminated Timber (CLT) Floors: Configurations in Lightweight Buildings

Cross-laminated timber (CLT) floors with supplementary layers or floating floors comprise a common solution in new multistory timber structures. However, bare CLT components provide poor sound insulation, especially in low frequencies during structure-borne sound propagation. Thus, floor configurations in wooden buildings deploy more layers for improved acoustic behavior. Twelve contemporary CLT floors were analyzed after laboratory measurements of airborne sound reduction and impact sound transmission utilizing the following indicators: Rw, Rw, 100, Rw, 50, Ln,w, Ln,w,100, and Ln,w,50 (per ISO 10140, ISO 717). An increase in sound insulation was achieved thanks to added total mass and thickness, testing layers of the following: elastic mat for vibration isolation, wool insulation, gypsum boards, plywood, concrete screed, and wooden parquet floor. The results indicate that multilayered CLT floors can provide improvements of up to 22 dB for airborne sound and 32 dB for impact sound indicators compared with the bare CLT slab. Floating floor configurations with dry floor solutions (concrete screed) and wooden parquet floors stand out as the optimal cases. The parquet floor provides a 1–2 dB improvement only for impact sound indicators in floating floor setups (or higher in three cases).

Horizontal impact sound transmission measurements

Impact sound transmission is typically considered for the floor/ceiling assembly that separates vertically stacked spaces. This is the context that ASTM E492 laboratory testing and ASTM E1007 field testing are performed. However, impact sounds often have the potential for causing significant flanking transmission through structural connections of the floor system to surrounding spaces. A common concern for possible impact sound transmission can occur with hard flooring finishes that are not isolated from the floor structure to adjacent spaces. For this condition, while it is possible to achieve adequate impact isolation vertically by using isolated ceiling assemblies, the lack of isolation for the flooring may allow significant horizontal impact sound transmission, which is not affected by the ceiling assembly. This study presents findings and comparisons from measurements of impact sound transmission testing between horizontally adjacent spaces on a concrete floor slab and a wood-framed floor assembly with different flooring underlayment conditions.

Comparative analysis of mechanical behaviour of glass fiber and rice husk reinforced composites

This survey paper is pointed toward featuring past works of RH-filled polymer composites give data to applications and further examination in this space. Based on the information gathered, using RH-filled composites as an alternative material in aircraft and boats is extremely feasible, with their major thrusts being lightweight and low effort. However, more research into physical and synthetic treatments to strengthen the interfacial binding with the polymeric network is needed, as the fiber-polymer link is critical in determining the final composite qualities. To understand the pre-owned polymer mixes as the grid and optional fillers may influence the properties would give fascinating territories to be investigated. In this study, rice husk was mixed with glass fibers in (50 + 50) and (25 + 50) weight percentage. A glass fiber and polymer were used as binder in 25% of the mass of the fillers. A sufficient number of small specimens were produced to perform small-scale tests and assess properties such as compressive strength, thermal conductivity, dynamic stiffness, improvement in impact sound insulation, sound absorption and transmission loss. Here the data based on the rice husk and glass fiber oriented composite analysis is carried out to bring a optimized fiber reinforced polymer composites.

Impact sound transmission: experiments of control at the receiver room

Considering Impact sound level requirements accomplishment in Brazil, floating floors are still considered as an inviable solution for building companies due to the implications in the total cost of building, mainly for social housing. Alternative and sometimes cheaper solutions are those undertaken in the receiver room. However, the lack of laboratory and field tests on the acoustic performance of this type of system is still a barrier for acoustic designing in Brazil. The aim of this paper is to study and validate different constructive solutions developed jointly with building companies for improving the impact sound insulation performance on the receiving room of new Brazilian housing constructions.

Impact sound prediction of finite floor structures with the modal transfer matrix method

The transfer matrix method (TMM) is commonly employed for wave propagation analysis in layered media of fluid, elastic and porous nature. Up to now it has been used extensively to analyze airborne sound transmission and sound absorption. Its use for impact sound transmission has been investigated to a limited extent, i.e. for thick homogeneous elastic plates of infinite extent and for specific receiver points. This contribution aims to broaden the scope such that the global impact sound, radiated by finite floor structures containing elastic, fluid and/or porous layers, can be analyzed in a more robust way than previously available in literature. A disadvantage of the conventional TMM is that only floors of infinite extent can be implemented. It is possible to remove this drawback using a spatial windowing technique. Furthermore, the modal behavior of the floor is approximately taken into account by projecting the impact force onto the mode shapes and only allowing for the propagation of those waves, corresponding to modal wavenumbers, in the structure. Predictions of the radiated sound power are made for various bare floors and floating floor systems of both infinite and finite extent.

Airborne and impact sound performance of modern lightweight timber buildings in the Australian construction industry

Timber usage in the Australian construction industry has significantly increased due to its strength, aesthetic properties and extended allowances recently introduced in building codes. However, issues with acoustic performance of lightweight timber buildings were reported due to their inherit product variability and varying construction methods. This article reviews the recent literature on the transmissions of impact and airborne sounds, flanking transmission of timber buildings, and the state of computer prediction tools with reference to the Australian practice. An in-depth analysis of issues and an objective discussion related to acoustic performance of timber buildings are presented. Timber is a lightweight material and shows low airborne sound resistance in low frequency range. Attenuation of sound transmission with addition of mass, layer isolation, different products like cross-laminated timber and prefabrication are discussed. Challenges in measuring sound transmissions and reproducibility of results in low frequency ranges are discussed. Well-defined measurement protocols and refined computer simulation methods are required. The serviceability design criteria for modern lightweight timber applications in Australia need to be re-evaluated in the area of impact generated sound. Developing computer tools to predict airborne and impact sound transmission in lightweight timber buildings is quite challenging as several components such as timber members and complex connections with varying stiffnesses are non-homogeneous by nature. Further, there is a lack of experimentally validated and computationally efficient tools to predict the sound transmission in timber buildings. Computer prediction tools need to be developed with a focus on mid-frequency transmission over flanks and low-frequency transmission of timber and prefabricated buildings.

Numerical simulation of impact sound transmission control across a smart hybrid double floor system equipped with a genetically-optimized NES absorber

An idealized detailed 2D formulation is presented for suppression of transient impact sound transmission across a hybrid smart double-leaf sandwich beam (floor-ceiling) structure into a rectangular (receiving) room with ideally flat and rigid walls. The smart double wall structure, which is mechanically inter-connected at an arbitrary point with a lightweight nonlinear energy sink (NES) absorber, incorporates spatially distributed and electrically independent non-collocated semiactive (electro-rheological fluid- or ERF-incorporated) and fully-active (piezoceramic- or PZT-incorporated) actuator layers functioning in a closed loop control framework. Extensive time-domain numerical simulations initially calculate both the uncontrolled and controlled transient acoustic pressure fields in absence of the dynamic vibration absorber for four separate settings of the active (PZT-) and semiactive (ERF-) actuation elements. Subsequently, the remarkable performance of the GA-optimized hybrid smart active/semi-active/passive (PZT/ERF/NES) configuration, which benefits from the multi-mode targeted energy transfer (TET) mechanism of the NES, in significant broadband (low frequency) attenuation of the transmitted shock energy with a much lower actuator energy demand, is demonstrated. Furthermore, some important aspects of the transient fluid-structure interaction (TFSI) control problem like weakening of the acoustic shock focusing effects (focal zones) within the source room are illustrated through selected early-to-late-times 2D images and animations of the cavity pressure fields. Limiting situations are studied and correctness of the derivations is established against accessible data in addition to numerical (FEM) simulations.

Numerical investigation of the sound-insulation effect of a suspended ceiling structure with arrayed Helmholtz resonators by the finite-difference time-domain method

In order to develop a numerical simulation of floor impact sound transmission via a floor structure that includes sound absorption materials, floor impact sound transmission via a composite floor structure composed of concrete slab, suspended ceiling plate, and an array of Helmholtz resonators inside a sandwiched air layer is modeled by the discrete wave-based numerical method of the vibroacoustic finite-difference time-domain (FDTD). As a preliminary study, the reverberant sound absorption coefficients of absorbers that contain arrayed resonators are simulated and compared to empirically measured values. The accuracy of the estimated sound absorption coefficient is found to depend largely on the diffuseness of the sound field in the simulated sound field as well as in reality. Thereafter, the floor impact sound generated by a floor structure that contains an array of resonators inside a sandwiched air layer between the floor slab and the ceiling plate is simulated, and relatively good agreement between the calculated and measured results for the improvement of the impact sound pressure levels caused by the installation of the resonators was confirmed. This suggests the applicability of the vibroacoustic FDTD method to sound-insulation prediction of the floor impact sound.

Acoustic performance of composite sandwich panels for building floors: Experimental tests and numerical-analytical simulation

Composite sandwich panels have been increasingly considered in structural applications due to their lightweight, high strength, environmental resistance, and ease of assembly. Yet, since transmission loss phenomena are usually governed by mass, their low weight renders composite sandwich panels potentially inefficient in terms of acoustic performance, a subject that has received little attention in the past. This paper presents experimental, numerical and analytical investigations about the acoustic performance of composite sandwich panels used in building construction. Standard airborne and impact sound transmission tests are performed on a full-scale composite sandwich panel, designed for structural application in building floors, and their acoustic performance is compared with the applicable code requirements. In the numerical study, a finite element model is developed to simulate the airborne sound transmission. The analytical study assesses the applicability of the reciprocity theorem to such panels. The obtained results confirmed the overall low acoustic performance of lightweight composite sandwich panel floors and pointed out the need for additional sound insulation measures. The numerical simulations presented good agreement with the experimental data, following the overall development of the experimental transmission loss curve, and predicting the dip associated with the coincidence effect. The application of the reciprocity theorem to the sandwich panel floors was validated with the experimental results and allowed for an accurate prediction of the impact sound pressure level based on the numerical results of the airborne sound reduction.

Low-frequency impact sound of timber floors: A finite element–based study of conceptual designs

Traditionally, product development concerning acoustics in the building industry is measurement oriented. For lightweight floors, frequencies that are lower than the frequency range for heavy concrete floors are an issue. The frequency range of from 50 Hz down to 20 Hz influences the human perception of impact sound in multi-story apartment buildings with lightweight floor constructions, such as timber floors, for example. It is well known that a lower frequency range of interest makes finite element simulations more feasible. Strategies for reducing impact sound tend to be less straightforward for timber floors because they have a larger variation of designs when compared to concrete floors. This implies that reliable finite element simulations of impact sound can save time and money for the building industry. This study researches the impact sound transmission of lightweight timber floors. Frequency response functions, from forces on excitation points to sound pressure in the receiving cavity below, are calculated. By using fluid elements connected to reflection-free boundary elements under the floors in the models, the transmission and insulation can be studied without involving reverberation. A floor model with a hard screed surface will have a larger impact force than a softer floor, although this issue seems less pronounced at the lowest frequencies. To characterize floor surfaces, the point mobilities of the impact points are also calculated and presented. The vibration and sound transmission levels are dependent on the selection of the excitation points.

Measurements of low frequency impact sound frequency response functions and vibrational properties of light weight timber floors utilizing the ISO rubber ball

Impact sound performance below 100 Hz forms part of a design criterion that is particularly important for multi-story timber buildings. An ISO tapping machine, which is predominantly used for impact sound measurement, has properties that may result in less measurement accuracy in the low frequency range, down to 20 Hz, than in its traditional measurement range above 100 Hz. The characteristics of the pistons’ impact are dissimilar to the impact of a human foot in this lower range. This may cause low signal-to-noise ratios in field measurements and the test data may also be less representative due to the test objects’ possible structural nonlinearities affecting impact sound transmission. The ISO rubber ball has shown to bear a close resemblance to a human’s excitation in the low frequency range, which makes it a suitable excitation device from this perspective. To support correlations between simulations and measurements, measuring impact forces in order to extract frequency response functions would be beneficial. To enable measurements of impact forces that stem from the ISO rubber ball, equipment for field measurements of forces and potentially point mobilities has been manufactured and evaluated. Furthermore, an investigation has been conducted into the repeatability of the rubber ball’s low frequency force spectrum for floors with different mobilities. Impact force measurements have been made on lightweight timber floors as well as on concrete floors. Within the frequency range up to around 55 Hz, it appears to be possible to use a prescribed force spectrum for the ISO ball, together with impact sound measurements, to create accurate impact force to sound frequency response functions for different floors. Also, instrumenting the impact point with an accelerometer enables estimates to be made of direct point mobilities.

Hard surface flooring policy for residential condominiums

A majority of the residential condominiums in the USA were originally constructed with wall to wall carpet flooring in the living rooms, bedrooms, and hallways. Removing the carpet and replacing it with various types of hard surface flooring is a recent popular trend. Converting these areas from carpet to hard surface flooring will result in a significant increase in impact sound transmission to the floor below as well as adjacent living units on the same floor. Unfortunately, some condominium homeowner’s associations do not have a written policy for accepting these modifications. Those that do often set the floor acceptance criterion as a field tested FIIC (now called AIIC) rating (typically in the 50 to 55 range), tested after the hard surface flooring is installed. This can result in significant financial impacts to the homeowner installing the flooring if final testing reveals that the floor does not meet the criterion set by the homeowner’s association. This presentation will discuss the complicated issues facing all three parties (homeowner, neighbor, and HOA Board) and presents a recommendation for a written policy that is fair to all.A majority of the residential condominiums in the USA were originally constructed with wall to wall carpet flooring in the living rooms, bedrooms, and hallways. Removing the carpet and replacing it with various types of hard surface flooring is a recent popular trend. Converting these areas from carpet to hard surface flooring will result in a significant increase in impact sound transmission to the floor below as well as adjacent living units on the same floor. Unfortunately, some condominium homeowner’s associations do not have a written policy for accepting these modifications. Those that do often set the floor acceptance criterion as a field tested FIIC (now called AIIC) rating (typically in the 50 to 55 range), tested after the hard surface flooring is installed. This can result in significant financial impacts to the homeowner installing the flooring if final testing reveals that the floor does not meet the criterion set by the homeowner’s association. This presentation will discuss the complicated ...

On the efficiency of impact sound insulation systems on prefabricated lightweight floor and on standard homogeneous base-floor

Considering the impact noise as a major social issue in many countries, extensive work have been developed aimed at reducing the noise level in dwellings. Laboratory tests were carried out to investigate the acoustic performance of same constructive proposals, arranged to reduce the impact sound transmission. According to this study, acoustic performance of both types of floors differs significantly, with a difference of up to four times that of the effect of floating floor system on a homogeneous floor in some cases. The conclusions can help to determine the proposal of best suitable constructive solutions in accordance with legal regulations.

Common problems associated with reverberation rooms in sound testing laboratories

Reverberation rooms have proven to be a very useful tool in acoustic laboratories for measuring the sound absorption of acoustic materials, airborne and impact sound transmission through building partitions, as well as measuring the overall radiated sound power level of a wide variety of sound sources. The primary benefit of a reverberation room is that the measurement can be made in much less time than with alternative environments (e.g., anechoic or hemi-anechoic chambers, or via acoustic intensity). The primary disadvantage of the reverberation room measurements is that all information regarding the directivity of the acoustic source is lost. This paper discusses some of the design and acoustical performance problems that are often found in reverberation rooms that could have been avoided with proper foresight. Issues that will be discussed include location relative to nearby noise and ground vibration sources, room size and shape, space planning for microphone locations, low frequency absorbers, and the importance of temperature and humidity control. Specific guidelines that should be followed when planning a new reverberation room will be provided.

Application of rice husk in the development of new composite boards

The main objective of the paper is to propose a new composite material incorporating rice husk. This paper reports an experimental study on the mechanical, thermal and acoustic performance of new composite boards made of rice husk waste intended for construction applications. In this study, rice husk was mixed with expanded cork granules or recycled rubber granules in 50/50 and 75/25 (weight percent) proportions. A TDI-based polyurethane pre-polymer was used as binder in 20% of the mass of the fillers. A sufficient number of small boards were produced to perform small-scale tests and assess properties such as compressive strength, thermal conductivity, dynamic stiffness, improvement in impact sound insulation, sound absorption and transmission loss.The results are very interesting, in particular: the thermal conductivity, at 10 °C, varies from λ10 = 60.0 mW/(m.K) to λ10 = 74.3 mW/(m.K); the weighted reduction of the impact sound pressure level, ΔLw, ranges from 20 dB to 27 dB; the noise reduction coefficient (NRC) ranges from 0.15 to 0.45, with maximum sound absorption coefficient of 0.96 for composite B1. These results suggest that optimized construction solutions based on these composite materials could improve the thermal and acoustic performance of buildings.