Abstract:
The understanding of the sound transmission mechanisms through suspended ceilings beneath concrete floors is today essentially of empirical nature, or originating from prediction models the level of simplificatlon of which is a significant obstacle to their widespread application. The prediction and control of sound transmission through suspended ceilings beneath concrete floors requires the knowledge of the forces, moments and sound pressures present within and acting on the structure. The interactions between the different components of such a floor are yet to be understood, particularly at low frequencies where the modal effects associated with the finite size of the structure need to be considered. By proposing a theoretical model describing these mechanisms, this thesis aims at providing a deeper appreciation of these components' contribution to the sound transmission. The finite dimensions of the structure a.re taken into consideration by adopting a modal approach whereby the displacements and pressure fields are expanded into infinite series of admissible functions. By expressing these quantities as functions of the displacement fields of the concrete floor and ceiling panel, coupling terms describing the interactions between the different components are obtained and from which a substantial amount of information is extracted. The coupled equations governing the motions and sound pressures within the structure are then written as a set of matrix equations, the only unknowns of which are the expansion coefficients for the displacements of the concrete floor and ceiling panel. Finally, the solutions are calculated numerically. It is shown that the solution is applicable to non-periodic geometries and thus opens the door to a new range of investigations on the dynamics of non periodic finite double plate structures. Once the model is experimentally validated, a parametric analysis is conducted on the effects of the material properties, the geometry and the design characteristics of the structure. The parameters that affect the most the sound insulation of the system are identified and their effects are quantified.
