The reduction of blast noise with aqueous foam

Abstract

Experiments were performed to investigate the potential of water-based foams to reduce the farfield noise levels produced by demolitions activity. Measurements of the noise reductions in flat-weighted sound exposure level (FSEL), C-weighted sound exposure level (CSEL), and peak level were made for a variety of charge masses, foam depths, and foam densities (250:1 and 30:1 expansion ratio foams). Scaling laws were developed to relate the foam depth, foam density, and charge mass to noise reductions. These laws provide consistent results for reductions in the peak level, FSEL and CSEL up to a dimensionless foam depth of 2.5. A two part model for the mechanisms of sound level reductions by foam is suggested.