Sound reduction index of dry-wall materials: Experimental comparison of model predictions and transmission room measurements

In the construction industry, it is often necessary to check the dynamic properties of the products and to relate them to their acoustic quality. A typical example is the production of building materials for the construction of dry walls. In this context, the availability of a quick, though reliable, method to be applied in-situ or to small portions of material can be of great help, both for quality control and for research and development purposes. Some relatively simple methods have been recently proposed, that start from the determination of the bending stiffness and the losses to estimate the acoustic insulation properties of the material, that is, the sound reduction index at different frequencies. In particular, the bending stiffness can be found either from the natural frequencies of beams cut from the product, or from the space average of the point mobility function measured on the whole leaf. Plasterboard is very popular because it is lightweight, modular and easy to install, its technical characteristics depending on thickness, type of facings and gypsum chemical composition. An interesting variant is offered by gypsum fibreboard, featuring considerably improved mechanical and water resistance properties. Plasterboard and gypsum fibreboard production is therefore an excellent test bench to assess the capabilities of the simple methods outlined in the literature. In this paper, the sound reduction indices obtained from both natural frequency and point mobility methods have been compared to measurements performed in double sound transmission room according to ISO 10140 series standards, to the aim of pointing out the potential and the limits of the two methods and setting the path for future developments. Tested materials include plasterboard and gypsum fibreboard.