Architectural Testing, Inc., an Intertek company (Intertek-ATI), was contracted to conduct airborne sound transmission loss and impact sound transmission tests. The complete test data is included as attachments to this report. The full test specimen was assembled on the day of testing by Intertek-ATI. All materials provided by the client were installed on an existing Intertek-ATI assembly (Cross Laminated Timber - 175 mm) utilizing Intertek-ATI-supplied.
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).
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.
The use of timber constructions recently increased. In particular, Cross Laminated Timber floors are often used in multi-story buildings. The development of standardization processes, product testing, design of details and joints, the speed of construction, and the advantages of eco-sustainability are the main reasons why these structures play a paramount role on the international building scene. However, for further developments, it is essential to investigate sound insulation properties, in order to meet the requirements of indoor comfort and comply with current building regulations. This work presents the results obtained by in field measurements developed using different sound sources (tapping machine, impact rubber ball, and airborne dodecahedral speaker) on Cross Laminated Timber floors, changing different sound insulation layering (suspended ceiling and floating floors). Results clearly show that the influence on noise reduction caused by different layering stimulated by diverse noise source is not constant and furthermore that no available analytical model is able to correctly predict Cross Laminated Timber floors acoustic performances.
The timber building industry is developing building systems for urban buildings with open architecture based on long span floor systems. Span length can be increased with constant cross section by combining stiff floor elements e.g. hollow-box floors with supports that provide high rotational stiffness. Detailed knowledge of the vibroacoustic behavior of such a system is not available and is needed to design buildings that fulfill the requirements in an economic and sustainable way. We set up a prototype and performed experimental investigations to identify the modal properties of such a system and to gain understanding of the sound radiation properties under impact excitation. The measurements were performed in an industrial hall using experimental modal analysis (EMA) and the Integral Transform method (ITM). The results highlight the limitation of standard acoustic laboratories and show the importance of using advance measurement methods to acquire reliable data. The size of the element and the boundary condition clearly affect the radiated sound power at low frequencies. Sound radiation can be efficiently reduced above 50 Hz by using traditional strategies such as gravel in the cavity of the floor elements. Additionally, insights about the ITM are presented, showing that symmetry cannot be exploited and that there is no requirement for a baffle when impact excitation is under investigation.