The Midply™ triple-leaf shear resistive wall is designed by FPInnovations and UBC to be employed in mid-rise wood building. Compared to double-leaf structures, this wall has a weaker low-frequency sound insulation due to the additional resonance created by the middle-leaf. The original contribution of this thesis is developing a method to predict the air-borne sound transmission through triple-leaf walls, which can incorporate perforated plates. The model is based on a modified Transfer Matrix Method (TMM) that accounts for the losses at the perimeter of the finite cavity. The air-borne sound transmission tests performed on simplified small-scale structures showed that the modified TMM model has acceptable predictions in most frequencies, although Statistical Energy Analysis (SEA) was superior for high-frequency predictions. The research suggests that the sound insulation in triple-leaf structures could be improved through careful perforation of the middle-leaf, which is suggested for future work.
Structure-borne sound transmission across a cross-junction of double solid timber walls with a solid timber floor was analyzed in a recent research project. Both, the double walls as well as floor slab, were of so-called Cross Laminated Timber (CLT). The floor slab was continuous across the junction for structural reasons and thus, formed a sound bridge between the elements of the double wall. To gain a better understanding of the contributions of sound transmission between the wall and floor elements from the different possible paths, a thorough analysis was conducted. Hereby, direct sound transmission through, and radiation efficiencies of, the CLT elements were measured in a direct sound transmission facility; as well as, structure-borne sound transmission between CLT elements was measured on a junction mock-up. The experimental data was used as in-put data and for validation of the engineering model of EN 12354/ISO 15712 for the prediction of flanking sound insulation in buildings. The test procedures, analysis and results of this research project are presented here.
The 2015 edition of the National Building Code of Canada (NBCC) includes significant changes to the acoustic requirements for residential constructions. The 2015 edition defines the acoustic requirements in terms of the Apparent Sound Transmission Class (ASTC) rating which includes contributions from flanking transmission and therefore is a better descriptor of how well the sound insulation of a building will actually protect the inhabitants of the building from unwanted noise than the STC rating which was used in earlier editions of the NBCC. The 2015 NBCC requires an ASTC rating = 47 for constructions between dwelling units.
The ASTC rating that a construction will achieve depends on the design of the building elements including the gypsum board, the framing and the thermal insulation as well as the design of the junctions between the building elements. Changes to the building elements or the junctions will change the ASTC rating.
Fifty five examples of the calculation of the ASTC rating for typical mid-rise wood constructions (single and triple staggered wood stud walls and floors constructed of I-joists) with 15.9 mm (5/8”) SilentFX® QuickCut gypsum board, 15.9 mm CertainTeed Type X gypsum board and CertainTeed Sustainable fiberglass insulation are presented. All of the constructions shown in the examples have an ASTC rating which is greater than 47.
In addition to the examples for mid-rise wood framing, an example using 15.9 mm SilentFX® QuickCut gypsum board as a lining on a cross laminated timber (CLT) construction is also presented.
The insulated predictions were carried out for LVL, CLT and HCLT in order to evaluate their sound properties, in which the theoretical value of sound insulation was predicted by regarding the substances in wood cell wall as equivalence to specific medium based on Biot model, and the wood anatomical characteristics, such as the length and diameter of tracheid, diameter of pit, and porosity, were taken into account for determining the equivalent density and bulk modulus of elasticity of wood cell wall. By comparing the tested and predicted values of sound insulation, the conclusion were drawn as follows: the predicted values of sound insulation were significantly correlated with the tested values for LVL, CLT and HCLT. As for Masson pine and Southern pine, the adjacent of earlywood and latewood was considered as sandwich structure for the calculation of sound insulation. Meanwhile, the bonding interface was creatively introduced to improve the accuracy of sound insulation prediction. The transfer function involved in sound insulation prediction provide an effective method to characterize the sound insulation volume of wood composite in construction and decoration areas.
The next generation of heavy timber building systems is about to transform the design and construction of many buildings in Australia.
Products that make up heavy timber construction include:
Cross-laminated timber (CLT)
Expan: post-stressed frames and box beams
Glulam and LVL beams, planks and floor systems
An engineered timber building product, CLT is widely used internationally, particularly in Europe. Although it is not currently widely used in Australia, the potential for its specification in dividing walls, floors and ceilings is increasingly evident, particularly for multi-storey residential buildings. These buildings have acoustic requirements, stipulated in Australia by the National Construction Code, Building Code of Australia (BCA) or by a relevant Local Government Authority.
Previous acoustic research programs covering CLT have been conducted in Europe and North America. The applicability of this data to the Australian market is limited due to the design of the testing to address codes that are not relevant to Australia. The overseas test elements also often include construction materials that are not available or not in widespread use here.
A previous Swedish research project indicated the potential need for evaluating impact sound insulation from 20 Hz in buildings with lightweight constructions. This is a discrepancy compared to the commonly used frequency intervals starting from 50 or 100 Hz. The statistical significance of this groundbreaking suggestion was however not satisfactorily strong since the result was based upon a limited number of building objects.
The scope of the present paper is to secure the previous study by adding additional objects to the underlying database, thereby increasing the confidence of the results. The methodology is to perform impact sound insulation measurements in apartment buildings of various construction types and to perform questionnaire surveys among the residents. The measured sound insulation is compared to the subjective rating by the occupants in order to find the parameter giving the highest correlation with respect to frequency range and weighting.
The highest correlation was found when the impact sound insulation was evaluated from 25 Hz using a flat frequency-weighting factor. Frequencies below 50 Hz are of great importance when evaluating impact sound insulation in lightweight constructions.
This cooperative project amongst CLT suppliers was initiated to develop base line information on the sound attenuation performance of CLT floor and wall systems. Further, to provide baseline sound attenuation information on CLT wall and flooring systems that will allow the development of:
1. Information for building professionals to meet building code requirements.
2. Information for acoustic consultants to develop assessments on variations to the baseline tested system.
In cross-laminated timber (CLT) buildings, in order to reduce the disturbing transmission of sound over the flanking parts, special insulation layers are used between the CLT walls and slabs, together with insulated angle-bracket connections. However, the influence of such CLT connections and insulation layers on the seismic resistance of CLT structures has not yet been studied. In this paper, experimental investigation on CLT panels installed on insulation bedding and fastened to the CLT floor using an innovative, insulated, steel angle bracket, are presented. The novelty of the investigated angle-bracket connection is, in addition to the sound insulation, its resistance to both shear as well as uplift forces as it is intended to be used instead of traditional angle brackets and hold-down connections to simplify the construction. Therefore, monotonic and cyclic tests on the CLT wall-to-floor connections were performed in shear and tensile/compressive load direction. Specimens with and without insulation under the angle bracket and between the CLT panels were studied and compared. Tests of insulated specimens have proved that the insulation has a marginal influence on the load-bearing capacity; however, it significantly influences the stiffness characteristics. In general, the experiments have shown that the connection could also be used for seismic resistant CLT structures, although some minor improvements should be made.
Cross Laminated Timber (CLT), which is well suited for construction of tall buildings, is becoming a more popular construction material in North America. However, to ensure comfortable living conditions, sound insulation measures are necessary. The study presented here compares results of direct impact sound insulation of 5- and 7-ply CLT floors covered with different a concrete toppings on various interlayers. Improvements of up to 21dB in Weighted Normalized Impact Sound Pressure Level (Ln,w) were observed using a newly proposed reference floor for CLTs. Furthermore, the improvements of floor coverings on CLT floors are compared to those achieved on other types of construction, such as the reference concrete floor. The improvements of Ln,w tend to be higher on the concrete floors than on the CLT floors tested. These and other findings will be presented.
Buildings constructed with cross-laminated timber (CLT) are increasing in interest in several countries. Since CLT is a sustainable product, it can help the building industry to reduce greenhouse gas emissions. Furthermore, buildings constructed with CLT are increasing in building height, thereby increasing the load on the junctions and structural building elements further down in the building. Several studies have investigated how the load impacts the sound transmission between apartments. The majority found that an increasing load could have a negative effect on the vertical sound insulation. However, the findings are limited to a few measurements or building elements, and the studies only investigate junctions with resilient interlayers. This article aims to investigate if the building height, and thereby the load, affect the vertical airborne sound insulation between apartments on different stories in different cross-laminated timber buildings, with or without the presence of viscoelastic interlayers, and to quantify the effect. Four CLT buildings with different building systems, building heights, and the presence of viscoelastic interlayers in the junctions were measured. The airborne sound insulation between different apartment rooms was measured vertically for stories on the lower and higher levels. The difference in airborne sound insulation was calculated separately for each building, and the measurements indicate that the vertical airborne sound insulation reduces further down in the buildings. Therefore, results show that increasing load, by an increasing number of stories, has a negative effect on the vertical airborne sound insulation.