Amplitude and Spectral Characteristics of Low Grazing Angle Acoustic Backscatter

摘要

Acoustic backscattering from the sea surface at grazing angles in the region of 5 degrees is affected by shadowing. Under these conditions the equations presented by Bass, Fuks, et al. (IEEE Transactions on Antennas and Propagation, vol. AP-16, no. 5, Sept. 1968) may be combined to form a single equation. The agreement between experimental data near 1kHz and the unified equations is good. The frequency shift of the backscattered acoustic energy is dependent on wave height and period through the horizontal orbital particle velocity. The frequency spread of backscattered energy is still dependent on the same particle velocity but is diminished because the wave troughs are preferentially insonified. The experimentally determined values of backscattering strength compare favorably with other reported low frequency, low grazing angle data.