Acoustic scattering and the spectrum of atmospheric turbulence

Some issues regarding atmospheric turbulence modeling and its role in acoustic scattering calculations are discussed. Discrepancies between turbulence spectral models appearing in the acoustical and in the atmospheric sciences literature are noted, and it is argued that these discrepancies can be understood by recognizing that the acoustic wavelength and scattering geometry combine to act as an "acoustic filter" which selects a specific part of the turbulence spectrum. A particular model spectrum can yield satisfactory acoustic scattering predictions if it fits the actual spectrum well at the acoustically filtered turbulence scales, even if the model is a poor overall representation of the turbulence spectrum. Proper interpretation of length scales determined by fitting two-point correlation functions, and the importance of averaging times in estimating variances, are also discussed in relation to the action of the acoustic filter. (C) 1999 Acoustical Society of America. [S0001-4966(98)03512-7].