Review of granular material damping and sound absorption for possible application in the sound insulation of lightweight floors
Yousif Badri, George Dodd, John Cater, Andrew Hall, Gian Schmid, Grant Emms, Emilio P. Calius
Abstract
Modern structures incorporating lightweight, low-stiffness floors face challenges for low-frequency impact noise transmission. Using spring isolators or resilient layers (e.g., floating floors) to improve isolation in light weight floor can introduce variability over time and increase structural complexity, making the system more sensitive to construction errors. An alternative approach is reviewed in this work, using internal floor cavities that contain Granular Materials (GM). Previous studies describe GM particle dampers in different applications where large movements between particles result in significant energy losses. However, a review of the experimental methods used in those studies is needed to be able to quantify the energy losses in relation to the type and degree of impact excitation. Modelling approaches are reviewed comparing their computational demand and which properties of GM are included, motion regimes and container properties. These studies span both destructive and non-destructive testing methods and give some pointers to both the geometrical and mechanical properties of granules which influence dissipation. This review goes beyond structural damping to include airborne sound absorption provided by a granular bed. This additional attenuation can be significant over a wide frequency range. A small number of practical studies of GM integrated with light weight floors show improvement in impact sound insulation. However, the lack of more detailed knowledge of GM damping mechanisms and a better understanding of GM bed interactions with containers prevents optimization of their use for insulating floors against sound transmission. This review proposes a general framework for future GM research to guide the selection of appropriate GM and addresses what is needed for optimizing lightweight floor impact sound insulation. • The review suggests impact sound insulation improvement of light weight floors through damping and sound absorption of Granular Materials (GM). • GM damping measurement methods are reviewed and classified by their inclusion of the host structure resonances. • Modelling approaches for GM damping are reviewed, comparing continuous and discretized theories for particle beds. • An overview of sound absorption spectra changes with particle size is presented, characterized by sound propagation theories in equivalent fluid and solid media. • Systematic steps for the addition of GM into lightweight floors are proposed, emphasizing the need for further research.