Influence of Wall Surface and Air Modelling in Finite-Element Analysis of Sound Transmission Between Rooms in Lightweight Buildings

Noise is a nuisance in the built environment, and to avoid undesirable transmission of sound and vibration within a building, its vibro-acoustic performance must be addressed in the design phase. For heavy structures, a reliable assessment of the sound pressure levels can be made by statistical energy analysis—especially at high frequencies. However, for lightweight buildings a numerical approach, e.g. the finite-element method, must be applied. A problem in this regard is the computational complexity. Even at low frequencies, many degrees of freedom are required in a model accounting for all possible paths for transmission of sound in a building—in particular when finite elements are employed for the air. This paper examines whether a rigorous model of the acoustic field in each room is necessary in order to obtain accurate estimates of the sound pressure, or if a simpler approach may be adopted. Five different cases are compared: A model that only includes the structure, a model with semi-infinite elements to account for radiation from the structure into the air, a model introducing finite elements for the acoustic field, a model with dissipation of sound inside the room, and finally a model with sound absorption on the surfaces of walls, floors and ceilings.