Attenuation of low‐ and high‐frequency waves in a random medium

Abstract

A theoretical analysis of the wavefield radiated by a point source in a one‐dimensional random medium has been carried out. Approximate expressions for the mean intensity and mean energy flux as a function of propagation range, based on general results obtained previously, have been derived for the limiting cases of low and high frequencies. These expressions show that, in both cases, the mean intensity and mean energy flux decrease more rapidly with range than would be the case in the absence or randomness. This more rapid rate of decrease with range can be interpreted as an excess attenuation. These results are similar, in general, to those obtained previously for the intermediate‐frequency case. The low‐frequency results are found to be in qualitative agreement with observations of excess attenuation of sound propagating through turbulence. At high frequencies, the results indicate that the excess attenuation is always much smaller than the attenuation due to absorption. This is also in agreement with observations, which generally show no significant excess attenuation at high frequencies. [Work supported by NORDA.]