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.

Prediction of nonlinear propagation of noise from a solid rocket motor

“…The measured spectra, shown as blue and black lines in Figs. 3 and 4, show that the measured spectra contain broad interference nulls around 180 Hz at 76 m, 125 Hz at 305 m, and 60 Hz at 1220 m. Although not exact, these nulls are reasonably predicted at the measurement locations from a monopole at the origin using the method of Embleton et al 23 and an effective flow resistivity of 10-20 gcs rayls appropriate for snow-covered ground. However, given the drastic quantitative differences between a monopole and a rocket noise source distribution, these interference effects are noted, but not included, in the predictions.…”

Variable response of anuran calling activity to daily precipitation and temperature: implications for climate change

“…In contrast, E. brittoni and E. juanariveroi call from the tips of the vegetation in the wetland (N. RiosLopez, personal communication). The preference for this calling site is likely related to their high frequency calls (.4.5 kHz), which would not transmit well from within the dense vegetation (Embleton et al 1983). These species are small (E. brittoni 14-19 mm; E. juanariveroi 12-17 mm), and it is possible that the impact of raindrops or the noise during period of high rainfall may forced them to move to lower strata within the vegeta-tion, and reduce or stop calling activity.…”

Ground effects in FAA's integrated noise model

“…al. Because of the extensive field measurement validation, performed at various values of effective flow resistivity, for source heights up to 1.8 m, receiver heights up to 1.5 m, and source-to-receiver distances up to 1097 m, conducted in support of its development 15,16 , the EPD implementation of this compilation of work was selected for INM development.…”