Sound Transmission in a Half Channel and Surface Duct
Technical note no. 2
METEOROLOGY INTERNATIONAL INC MONTEREY CA
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The normal mode solution of sound transmission has been used as the basis of an approximate WKB calculation. The attenuation of low frequency signals in a surface duct is shown to be proportional to f to the -53rds power where f is the frequency. The high frequency attenuation is based upon experimental data and is proportional to sq. rt. of f. The leakage of sound energy from the duct is used as a means to estimate the signal received beneath the duct. The theoretical results have compared with theoretical data. The surface duct attenuation formula fits the experimental data within the spread of the data.