ON A SIMPLIFIED PREDICTION MODEL OF THE DYNAMIC MOBILITY OF SOLID BUILDING ELEMENTS WITH EXPERIMENTAL VALIDATIONS

Standard EN 12354-5 describes the prediction method of the noise due to building equipment. The characteristics of the noise source and the connected building element can be determined according EN 15657, which suggests using a point mobility of an infinite homogeneous plate as the mobility of the building element. However, this characteristic mobility is frequency constant, and differs at low frequencies significantly from the dynamic mobility of the finite plate, particularly near the boundaries. Such an oversimplified model leads to the incorrect estimation of the noise from building equipment. To improve the accuracy without deteriorating its simplicity, a simplified dynamic model is developed, in which the mobility at low frequencies is expressed as a linear function of frequency, while the mobility at mid and high frequencies is still determined by the frequency-constant model. The linear mobility function relies on the material and the geometry of the plate, the location of the source on the plate and the supporting structures affecting the boundary conditions. In particular, this paper focuses on the effects of locations and boundary conditions on the gradient of the linear mobility functions. This simplified prediction model was validated with the measured dynamic point motilities of several building elements.