Optimization of the acoustic performances of lightweight sandwich roof elements

Lightweight roof elements are commonly used in buildings because of the ease and speed of installing and the potential for very high and reliable thermal insulation. The sound insulation of the sandwich panels however may be too low. In fact, the combination of low mass and high stiffness typically results in a lower sound transmission loss over a large frequency band. But regularly the presence of higher outdoor levels is reflected in stricter requirements, so making improvements on the sound insulation of these roof elements necessary. The sound transmission loss of different lightweight sandwich panels with a core of expanded polystyrene has been measured in the lab. Also the structure-borne sound sensitivity has been measured with a mini-tapping machine. These measurements are compared with an analytical model based on the transfer matrix method and a numerical, wave based model. Primarily the influence of geometrical size of the panel and of the composition of the interlayer is discussed in view of optimizing the results.