Abstract
The noise and meteorological data acquired by the Air Force AMRL at Wright-Patterson Air Force Base has been analyzed to determine the factors most influencing the excess sound attenuation at different frequencies and distances. Multiple regression analyses of the excess sound attenuation (the difference in noise levels measured at different positions referred to the reference position levels after adjustment for inverse square and air absorption losses) indicate that the strongest variables influencing the excess sound attenuation are the wind component in the direction of sound propagation, the temperature gradient, and the ground cover (grass versus snow). Regression coefficients ranged up to the order of r2 = 0.8. Plots of the variance accounted for (r2) values as a function of frequency show two distinct peaks which shift downwards in frequency as distance increases. At low frequencies (below about 200 Hz), the most significant variable is ground cover. For the higher frequencies the most significant variable is the wind component. Curves showing the measured excess attenuation values as a function of wind component and temperature gradient will be compared to results from other studies and theoretical models.
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