Acoustic absorption in re-cycled rubber granulate

The use of recycled rubber in the production of noise barriers can help combat the existing problems of both waste disposal and noise pollution. It is suggested that the physical characteristics of rubbers are advantageous over other materials currently available. Comparisons are made between unconsolidated 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 smaller grain sizes, although absorption is observed to increase in materials made up of larger grains. It is shown that the relationship between the two states can be partly described by the change in flow resistivity and first resonant frequency. This, in turn, allows for the prediction of a consolidated material's acoustic properties to be made. It also helps in optimising 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 frequency. (C) 1998 Elsevier Science Ltd. All rights reserved.