On the modeling of multilayer systems with mechanical links

Multilayer systems are widely used for sound transmission insulation and generally have mechanical links to ensure their strength and/or rigidity. Double leaf structures with mechanical links are commonly used in buildings or in transportations (railways, aeronautics, etc...). Several analytical models already enable to take into account both the air-borne and the solid-borne paths of the sound transmission. Nevertheless, these latter only consider the solid-borne path for a single mechanical link with thin plates on both sides. Condensed equivalent plate models can be used to extend these models when thin multilayers are placed on one side of the mechanical link. But, they do not allow to take into account thick multilayers, especially if they exhibit a resonant behavior such as a spring-mass system. This work proposes a methodology which takes into account any multilayer systems on both sides of mechanical links, including solid, fluid, poro-elastic isotropic or orthotropic layers. First the admittances are computed on each side of the mechanical link. Then, the mechanical links are modeled by a structural transfer matrix. Finally, the solid-borne path can be computed in addition to the air-borne path. All these computations are based on transfer matrix method and wavenumber decomposition. The proposed model also enables to handle stuctures with several mechanical links in series. The model is compared to existing models and to experiments for double leaf partitions with a single mechanical link and thin panels. Then, results will be presented for more elaborated configurations with thicker multilayers or several mechanical links.