Acoustic absorption in re-cycled rubber granulate

The use of recycled rubber in the production of noise barriers can help com bat the existing problems of both waste disposal and noise pollution. It is suggested that the physical characteristics of rubbers are advantageous ov er other materials currently available. Comparisons are made between uncons olidated rubber crumb and crumb consolidated with an adhesive for different sized grains and material thicknesses. The studies show that the effect of reducing the overall absorption by applying an adhesive is increased in sm aller grain sizes, although absorption is observed to increase in materials made up of larger grains. It is shown that the relationship between the tw o states can be partly described by the change in flow resistivity and firs t resonant frequency. This, in turn, allows for the prediction of a consoli dated material's acoustic properties to be made. It also helps in optimisin g a material's acoustic properties so as to yield the highest overall sound absorption and even tune the material to absorb sound at a desired frequen cy. (C) 1998 Elsevier Science Ltd. All rights reserved.