Structural sound transmission and attenuation in lightweight structures

Doctoral thesis, 2008

Everyone wants a peaceful and quiet home, but in noisy cities it is a challenge to create such homes. New building techniques are mostly introduced for other purposes than noise control -- stability, economy, heat transfer and so on. Then, it happens that sound insulation will suffer, most often because it is difficult to predict the sound insulation in buildings. The sound insulation is not known until measured after the building is finished. For some years now it has been more popular to build large houses with lightweight building techniques, especially with wood. This thesis aims toward better understanding of sound insulation in lightweight buildings. Some features related to sound insulation in lightweight buildings are examined. The vibration pattern is measured for a junction in a lightweight building. A simplified lightweight structure is analysed theoretically with use of Fourier series. Both studies focus on the attenuation rate, i.e. the rate at which the vibrations spatially decrease. The research shows that the attenuation rate is high in the direction across beams. In the direction along the beams there is not much attenuation. The attenuation rate depends on several parameters, especially vibration frequency and structural stiffness. Very high attenuation is observed for wavelengths longer than the distance between the beams. The hope is that this knowledge together with other studies will advance the understanding of lightweight structures so that a new prediction tool can be developed.