## Predicting the sound insulation of building elements – A model based on a transfer matrix scheme with some add-ons.

Tor Erik Vigran

NTNU–Acoustics Group, Dept. of Electronics and Telecommunications, O.S. Bragstads pl. 2, NO-7491 Trondheim, Norway

vigran@iet.ntnu.no

A large number of prediction models for the sound insulation of building elements, massive as well as multilayered types exist in the literature of which many are applicable for special constructions only. The transfer matrix technique is an efficient tool for calculating sound transmission through multilayered structures and recent windowing technique, accounting for finite size specimens, has greatly improved the fit to measurement data. Another improvement is presented in this paper allowing for the calculation of the effect of structural connections, e.g. studs, in double-leaf partitions, where the flexibility of the studs is a parameter. A number of comparisons with measured results will be presented, among them data for lightweight double plasterboard walls. Cases include walls with cavity filling as well with empty (air-filled) cavities.