This paper deals with a certain type of C.L.T. (Cross Laminated Timber) construction, in a residential building in Fristad, Sweden. The objective is to study impact noise transmission, at the lower frequency range (10-200 Hz), where wooden dwellings perform inefficiently, in terms of acoustic quality. The vibrational behavior of lightweight structures and specifically a multilayered floor separating two vertically adjacent bedrooms are investigated. A numerical model of the multilayered test plate, which includes sound insulation and vibration isolation layers, is developed using the Finite Element Method (F.E.M.) in commercial software. The design process, the analysis and improvement of the calculated outcome concerning accuracy and complexity are of interest. In situ vibration measurements were also performed so as to evaluate the structures dynamic behavior in reality and consequently the validity of the modelled results. The whole process from design to evaluation is discussed thoroughly, where uncertainties of the complex F.E.M. model and the approximations of the real structure are analyzed. Numerical comparisons are presented including mechanical mobility and impact noise transmission results. The overall aim is to set up a template of calculations that can be used as a prediction tool in the future by the industry and researchers.
There is a strong trend to industrially produce multi-storey light weight timber based houses. This concept allows the buildings to be manufactured to a more or less prefabricated extent. Most common types are volume/room modules or flat wall and floor modules. When assembling the modules at the building site, elastomer isolators are used in several constructions to reduce flanking transmission. The sound insulation demands in the Nordic countries are relatively high and therefore the flanking transmission must be well controlled, where elastomer isolators are an alternative. Decoupled radiation isolated walls is another. There are though no working studies or mathematical models of the performance of these isolators. They are only treated as simple mass-springs systems that operate vertically, i.e. one degree of freedom. In this paper there is an analysis of experimentally data of the structure borne sound isolating performance of elastomer isolators that are separating an excited floor from receiving walls. The performance dependence of structure type is also presented. An empirically based regression model of the vibration level difference is derived. The model is based on measurements of six elastomer field installations, which are compared to five comparable installations without elastomers. A goal is that the model can be used for input in future SEN prediction models for modeling of sound insulation.
This paper presents the first results of the flanksound project, a study promoted by Rotho Blaas srl regarding flanking transmission between CLT panels jointed with different connection systems. The vibration reduction index Kij is evaluated according to the EN ISO 10848 standard by measuring the velocity level difference between CLT panels. The performance of the X-RAD connection system is compared to the performance of a traditional connection system made of shear angle bracket and hold-down, both the configurations being tested with and without a resilient material placed between the construction elements. Concerning the traditional system, the influence of the difference sizes and types of fasteners - including the method of nailing or screwing - was also evaluated. The results of the measurements exposed in this work will hopefully contribute to the development of the acoustic design of timber buildings by providing a solid database of Kij values, which can be used to forecast the acoustic performance of the building according to the prediction models proposed in EN 12354-1.
The objective of this work package is to provide an acoustic performance knowledge database of European timber building constructions. In a first step a methodology for structuring the planned data base will be developed. The database will be fed with existing examples from the different European timber building regions. These examples will be grouped into similar solutions and sound insulation performance. After reprocessing the data the different construction systems will be optimized in WP 2.
An interface to the borad public of the database will then be developed. This user friendly and appealing front-end of the European Timber Sound Insulation Atlas (EATSI-Atlas) will provide information on various evaluation criteria, including expected future European target values.
This report comprises reslts from the work done within work package 1 in the WWN+ project "Silent Timber Build", WP 1: Prediction tools, low and high frequencies. The aim from this WP was to develop prediction tools applied for wooden constructions. Included in this is also to create necessary basis for enough accuracy for any European wood construction. It implies development of new methods but also to understand how input forces primarily from the tapping machine affects the resuts of impact sound levels. The WP also describes how models are developed, in order to provide expected accuracy and then how to further improve the models in order to optimize floor and wall assemblies. The Work Package has been closely linked to WP 2 but also WP3. Using the reults from WP 2, the prediction model results can be compared to expected values for any European construction. From that optimization of floor assemblies and refining of the model is possible.
In recent years Cross Laminated Timber (CLT) was introduced as an emerging building system in the North American market. CLT elements consist of multiple layers of wooden beams that are laid-out cross-wise and laminated together to form solid wood panels for floors and walls. As part of a multi-disciplinary research project a comprehensive study was conducted on the impact and airborne sound insulation of this type of elements in order to create a data base that allows building designers to predict the acoustic performance of CLT systems. Parametric studies were carried out on the direct impact airborne sound insulation of CLT floor assemblies (with/ without various floor topping and gypsum board ceiling variants), on the direct airborne sound insulation of CLT walls (with/without gypsum board linings), as well as on the structure-borne sound transmission on a series of CLT building junctions. The results were then used as input data for predictions of the apparent impact and airborne sound insulation in real CLT buildings using the ISO 15712 (EN12354) framework that was originally developed for concrete and masonry buildings. The paper presents the prediction approach as well as results of prediction and measurement series for apparent impact and airborne sound insulation.
This Report presents the results from experimental studies of airborne sound transmission, together with an explanation of calculation procedures to predict the apparent airborne sound transmission between adjacent spaces in a building whose construction is based on cross-laminated timber (CLT) panels.
There are several types of CLT constructions which are commercially available in Canada, but this study only focused on CLT panels that have adhesive between the faces of the timber elements in adjacent layers, but no adhesive bonding the adjacent timber elements within a given layer. There were noticeable gaps (up to 3 mm wide) between some of the timber elements comprising each layer of the CLT assembly. These CLT panels could be called "Face-Laminated CLT PAnels" but are simply referred to as CLT panels in this Report.
Another form of CLT panels has adhesive between the faces of the timber elements in adjacent layers as well as adhesive to bond the adjacent timber elements within a given layer. These are referred to as "Fully-Bonded CLT Panels" in this Report.
This report documents apparent/field impact insulation class (AIIC/FIIC) ratings and apparent/field sound transmission class (ASTC/FSTC) ratings for a large number of light-frame wood-joisted floors, cross-laminated timber floors (CLT), massive glulam floors, and a wood-concrete composite floor. The report includes various construction details involving finishings, membranes under finishings, toppings, underlayment materials for toppings, and drywall ceilings. This report also documents ASTC/FSTC ratings for some light-frame wood stud walls and CLT walls.
The informal subjective evaluation of field floors and walls by FPInnovations staff, and by occupants, revealed that, if a FSTC or FIIC rating is below 45, occupants could clearly hear sound generated by their neighbor’s normal activities. If a FSTC or FIIC rating is above 50, occupants could still hear "muffled" sound generated by their neighbor’s normal activities, but do not hear it as clearly. If a FSTC or FIIC rating is above 60, occupants could not hear any sound generated by their neighbor’s activities, except when there is a lightweight floor with a carpet. In that case, low frequency footsteps could be heard even if the FIIC was above 60.
The number of occupant complaints received about annoying low-frequency footstep impact sound transmission through wood floor-ceiling assemblies has been increasing in proportion with the increase in the number of multi-family wood buildings built. Little work has been conducted to develop solutions to control the low-frequency footstep impact sound transmission. There are no code provisions or sound solutions in the codes. Current construction practices are based on a trial and error approach. This two-years project was conducted to remove this barrier and to successfully expand the use of wood in the multi-family and mid- to high-rise building markets. The key objective was to build a framework for the development of thorough solutions to control low-frequency footstep sound transmission through wood floor-ceiling assemblies.
Field acoustic tests and case studies were conducted in collaboration with acoustics researchers, builders, developers, architects, design engineers and producers of wood building components.
The field study found that:
1. With proper design of the base wood-joisted floors and sound details of the ceiling:
With no topping on the floor, the floor-ceiling assembly did not provide sufficient impact sound insulation for low- to high-frequency sound components ;
Use of a 13-mm thick wood composite topping along with the ceiling did not ensure satisfactory impact sound insulation;
Even if there was the ceiling, use of a 38-mm thick concrete topping without a proper insulation layer to float the topping did not ensure satisfactory impact sound insulation ;
A topping system having a mass over 20 kg/m2 and composed of composite panels and an insulation layer with proper thickness achieved satisfactory impact sound insulation.
2. The proper design of the base wood-joisted floors was achieved by the correct combination of floor mass and stiffness. The heaviest wood-joisted floors did not necessarily ensure satisfactory impact insulation.
3. Proper sound ceiling details were found to be achieved through:
Use of two layers of gypsum board;
Use of sound absorption materials filling at least 50% of the cavity ;
Installation of resilient channels to the bottom of the joists through anchoring acoustic system resulted in improved impact sound insulation than directly attaching the resilient channels to the bottom of the joists.
A four-task research plan was developed to thoroughly address the issue of poor low-frequency footstep impact insulation of current lightweight wood floor-ceiling assemblies and to correct prejudice against wood. The tasks include: 1) fundamental work to develop code provisions; 2) expansion of FPInnovations’ material testing laboratory to include tests to characterize the acoustic properties of materials; 3) development of control strategies; and 4) implementation.
The laboratory acoustic research facility built includes a mock-up field floor-ceiling assembly with adjustable span and room height, a testing system and a building acoustic simulation software.
The preliminary study on the effects of flooring, topping and underlayment on FIIC of the mock-up of the filed floor-ceiling assembly in FPInnovations’ acoustic chamber confirmed some findings from the field study. The laboratory study found that:
A topping was necessary to ensure the satisfactory impact sound insulation;
The topping should be floated on proper underlayment;
Topping mass affects impact sound insulation of wood framed floors;
A floating flooring enhanced the impact sound insulation of wood framed floors along with the floating topping.
It is concluded that:
1. even if the studies only touched the tip of the iceberg of the footstep impact sound insulation of lightweight wood-joisted floor systems, the proposed solutions are promising but still need verification ;
2. with proper design of the base wood floor structure, the proper combination of flooring, and sound ceiling details along with proper installation, the lightweight wood floor-ceiling assembly can achieve satisfactory impact sound insulation ;
3. this study establishes a framework for thoroughly solving low-frequency footstep impact sound insulation problem in lightweight wood-joisted floor systems.
Solutions will be developed in the next phase of this study as planned and the study will be conducted under NRCan Transformative Technology program with a project dedicated to “Serviceability of next generation wood building systems”.
This report summarizes the acoustics research component regarding sound insulation of elements and systems for the research project on mid-rise and larger wood buildings. The summary outlines the background, main research considerations, research conducted and major outcomes. Further details of the design and the results can found in the appendix of Client Report A1-100035-02.1 .
The goal of the acoustics research components was to develop design solutions for mid-rise wood and wood-hybrid buildings that comply both with the current National Building Code of Canada (NBCC) 2010  requirements for direct sound insulation and with the anticipated requirements for flanking sound transmission in the proposed, 2015 version of the NBCC. In addition, the design solutions were to provide better impact sound insulation while still achieving code compliance for all other disciplines (interdependencies) as identified in the final report of the scoping study conducted in FY 2010/2011