A method for determining the sound reduction index of precast panels based on point mobility measurements

Precast panels are widely used for the construction of large industrial buildings, trade centres and apartment houses. These buildings have to comply with prescribed noise and thermal requirements, so the possibility to accurately estimate the sound reduction index of such panels is of vital importance. The sound reduction index can be determined through measurements carried out in a laboratory or on an already mounted real-scale panel, but both solutions present problems. For example, precast structures consisting of two concrete panels coupled via an interlayer can be very bulky and heavy, and measurements in standard sound transmission laboratories may be impossible to carry out. In some countries, predictions based on theoretical models are accepted in lieu of measurements. Following this approach, the application of simple models, not accounting for the influence of coincidence and of losses, is not sufficient to make acceptable predictions. In this paper, an alternative method to estimate the sound reduction index of precast panels is proposed. Different panels have been considered in the study, each of which has been modelled by a mathematical representation found in the literature. It will be shown that all of these models can be synthesised by a common mathematical formulation, allowing the sound reduction index to be determined from point mobility measurements. The effectiveness of the new method has been investigated by comparing predicted and measured results, obtained in a sound transmission laboratory satisfying existing ISO standards.