Effective flow resistivity of ground surfaces determined by acoustical measurements

Abstract

Following earlier work by Chessell [J. Acoust. Soc. Am. 62, 825–834 (1977)] it is shown that his single-parameter theory can be used to predict the measured transmission spectra between a source and receiver located above ground surfaces having a wide range of acoustic impedance—or effective flow resistivity. Surfaces behaving essentially as locally reacting range from new-fallen snow, effective flow resistivity σ=10–30 cgs rayls, through grass-covered ground, σ=150–300 rayls, to mature asphalt, σ=30 000 rayls. The thermal-conduction and viscous boundary layer of the surface limits the effective flow resistivity of even the hardest and most impervious surface to the range 105–106 rayls, depending on frequency: this value is appropriate to evaluate the complex reflection coefficient of the paint-sealed surface of a thick slab of reinforced concrete.