차주파수 음파를 이용한 수중모래 퇴적물에서 비선형 변수 추정

Abstract

Difference frequency acoustic wave from nonlinear interaction of two primary acoustic waves at frequencies of 76 and 114 kHz was utilized with a parametric acoustic array theory to estimate the nonlinearity parameter of water-saturated sandy sediment. Such nonlinearity parameter can be used as background information for the nonlinear acoustic investigation of bottom or sub-bottom profiling in the ocean sandy sediments. Because of its lower attenuation the difference frequency acoustic wave method can be usefully applied to estimate the nonlinearity parameter of ocean sediment in the ocean as well as under laboratory conditions. The nonlinearity parameter β for the water-saturated sandy sediment used as a reference in this study was estimated as β = 80.5 ± 5.1 at the difference frequency of 38 kHz. It was agreed very well with that estimated at the difference frequency of 67 kHz, when two primary frequencies were 137 and 204 kHz. The estimated nonlinearity parameter of water-saturated sandy sediment in this study was also compared and analyzed with those estimated in previously published literatures. It was suggested thatthe difference frequency wave method used to estimate the nonlinearity parameter of watersaturated sandy sediment can be employed as a good method to estimate the nonlinearity parameters of fluid-like granular media.