An Assessment Of The Effects Of Sound Speed Fluctuations On Sound Propagation In Shallow Water Using A Perturbation Method

Abstract

Abstract : Scintillations in the intensity of an acoustic signal are a common feature of propagation of sound in the sea, manifesting temporal variability in the index of refraction (sound velocity) of the medium. In this paper, a recently developed high-order perturbation method is described and applied to the problem of sound propagation in the sea. The method uses a canonical solution (sound speed profile) to form a set of basis functions that span the solution space and adequately represent the exact eigenvalue problem. The basis functions used in the calculations are derived from sound speed profiles obtained in an acoustic propagation experiment conducted in a shallow-water region of the Mediterranean. At particular source frequencies, calculations of modal functions and acoustic transmission loss were compared for the mean and several perturbed profiles. The results confirm the significant effects on acoustic transmission of seemingly minor variations in sound speed and, moreover, demonstrate the efficacy of the new perturbation method in handling such problems.