
AkuTimber – Low-frequency sound insulation in wooden buildings
In this project, the work comparing measured sound insulation parameters with survey responses based on residents' experiences, continues. Impact sound insulation at low frequencies, 20–50 Hz, is in focus as previous projects (Aku20 and AkuLite) have shown its importance for wooden buildings. In addition, innovative solutions with the potential for improved low-frequency sound insulation are studied.
LTU - Engineering Acoustics runs the research project in collaboration with LTU - Wood Science Engineering and Simmons Acoustics & Development. AkuTimber, which is our common name for two research projects funded by the Swedish Energy Agency and Formas, runs 2019–2022.
Existing Swedish sound insulation requirements between apartments do not take into account frequencies lower than 50 Hz, and internationally it is most common to set the limit to 100 Hz. In a market where the proportion of multi-family buildings in wood is increasing, it is relevant to review today's requirements as the acoustic response of wooden buildings is different compared to heavier building frames, e.g. I concrete. The most important differences, which also relate to how humans perceive sound, concern the lowest frequencies.
The project contributes to expanding a previously developed database. Measurement data from a total of 38 building cases with varying construction techniques will be included together with over 1200 survey responses from residents in the areas. With this data, evaluation parameters for airborne and impact sound insulation will be proposed with the possibility of including frequencies as low as 20 Hz.
Lightweight building systems, including wood-based ones, are difficult to design and construct for effective protection against low frequencies. Therefore, innovative methods are needed. The project draws on the popular concept of cross-laminated timber (CLT). Different CLT configurations will be tested within the project. One example is to use compressed wood whereby the mass of the panel can be increased dramatically maintaining the same thickness. The higher density of compressed wood is expected to be a positive contributing factor to the sound insulating ability. Also, CLT panels equipped with built-in elastic layers dimensioned with respect to shear movements, will be tested and evaluated.
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