Title :
Coupled scattering and reflection measurements in shallow water
Author :
Holland, Charles W.
Author_Institution :
SACLANT Undersea Res. Centre, La Spezia, Italy
fDate :
7/1/2002 12:00:00 AM
Abstract :
The characteristics of shallow-water reverberation are often controlled by scattering from the seabed. While scattering mechanisms are understood in general, the state-of-the-art falls far short of predicting the correct angular and frequency dependence of scattering in a given region. A series of acoustic and supporting geoacoustic measurements were conducted over a large area in the Straits of Sicily in order to study seabed scattering in a complex littoral environment. The hypothesis was that exploiting direct path reflection coefficient measurements, in conjunction with the scattering measurements, could help illuminate the underlying scattering mechanisms. The sediment at the seabed interface was found to be a fine silty clay with nearly uniform properties across the area. Notwithstanding this spatial homogeneity, 1-6-kHz reflection and scattering measurements showed significant spatial variability. The coupled reflection-scattering approach resolved this apparent discrepancy, revealing that the reflection and scattering processes are largely controlled by the sediment properties below, rather than at, the water sediment interface. Measurements at 3600 Hz show that site-to-site variability is in part controlled by the thickness of the silty-clay layer. Layers up to 10 m below the water sediment interface contribute to the scattering at 3600 Hz.
Keywords :
acoustic wave reflection; acoustic wave scattering; reverberation; sediments; underwater sound; 1 to 6 kHz; 3600 Hz; acoustic reflection; acoustic scattering; coupled geoacoustic measurements; reflection coefficient; seabed scattering; shallow water reverberation; silty clay; water-sediment interface; Acoustic measurements; Acoustic reflection; Acoustic scattering; Area measurement; Frequency dependence; Process control; Reverberation; Sediments; Spatial resolution; Underwater acoustics;
Journal_Title :
Oceanic Engineering, IEEE Journal of
DOI :
10.1109/JOE.2002.1040930