Estimation of gassy sediment parameters from measurements of angular and frequency dependencies of reflection coefficient

Method of upper gassy sediment layer characterization is proposed, based on measurements of angular and frequency dependencies of reflection coefficient, using wideband signals. Experiments were carried out in Lake Kinneret (Israel) with maximal depth ∼ 40 m, where the sediment contains gassy layer. Direct observations of gas void fractions in frozen sediment cores show layer’s thickness of a few decimeters. In our experiments wideband signals of 300–2000 Hz were used. Sound was recorded by single hydrophone located at 1 m distance from the source and by the Vertical Line Array of ten hydrophones placed a few tens of meters apart and deployed at the lake center. Estimation of gassy layer parameters was based on the reflection coefficient measured as a function of frequency and angle of incidence. In particular, for the depth of the lake ∼38 m half-wavelength resonances were registered, where resonance frequencies are 750 Hz and 1450 Hz that correspond to the thickness of gassy layer of 20 ± 5 cm, with the...