Sound Attenuation in a Sandwich Floor

Delphine Bard , Anders Sjöström

New Zealand Acoustics, 24(3), pp.15- 20 . (2011).

In modern building construction, where light weight structures are preferred for cost reasons, the sound transmission is often a problem to be considered carefully, hence the many studies addressing this issue. A common floor construction in a lightweight building system is using chipboard plates attached to wooden beams by screws and glue. One drawback with such a system is the propagation of vibrations stemming either from harmonic excitation like surround systems especially at low frequencies and/or transient excitation like human walking. In order to accurately predict the sound attenuation and the losses of such building systems, computationally accurate and efficient simulation techniques are needed. The main objective of the present work is to examine sandwiched floor constructs consisting of one and two layers of chipboards attached to supporting wooden beams. Discontinuities between adjacent boards and between boards and beams are of special interest. On one hand, they affect the kinetic energy loss, due to the acoustic attenuation of evanescent waves in the structure. On the other hand, they also alter the phase shift of the waves as they travel past the different types of discontinuities in the floor assembly. A series of measurements have been performed using two-axis accelerometers distributed over the floor and recorded synchronously. A special focus has been put on investigating the low frequency range (10-600Hz), including transient loads.