Vertical Array Receiver Research Articles

Modeling and interpretation of bistatic bottom reverberation in deep water near seamounts.

The received reverberation signal can be beamformed by utilizing a vertical array, generating a vertical-angle time record (VATR) that enables analysis of spatiotemporal distribution characteristics. Due to the influence of multipath propagation effects, deep-sea reverberation exhibits highly complex characteristics, especially in a seabed with significant depth variation. In a recent bistatic reverberation experiment with a vertical array receiver, peculiar bright stripes were observed in the VATR. These stripes are the result of scattering caused by large-scale bottom structures and are closely associated with seamounts. To accurately model and interpret these stripes, a bistatic reverberation model is initially established to reproduce the VATR. This model enables us to numerically simulate the spatiotemporal distribution of reverberation in the VATR, offering a qualitative explanation for these stripes. However, the model alone is incapable of predicting the specific stripe structure associated with a particular seamount. To address this limitation, an equation system is introduced to calculate the stripe parameters based on the seamount parameters. By analyzing and deducing the dependency of the stripes on the seamount, conclusions were drawn using the equation system. Ultimately, the presented model and equation system successfully reproduce and comprehensively explain the observed abnormal stripes from the experiment.

A look at reverberation received on a vertical array during the TREX13 experiment

The TREX13 Target and Reverberation Experiment was conducted in shallow water off Panama City, Florida. Previously published work focused on reverberation from a fixed horizontal array, which resolves scattering in the azimuthal direction, but has very limited information about the vertical dependence of the scattering. Here, we look at the TREX13 datai—LFM pulses of various bandwidths in the 1.8–3.6 kHz frequency range—received on the vertical line arrays (VLAs) to see what information can be gleaned. The depth and time dependence of the reverberation and echo from a target are investigated. Beams are formed at various vertical angles, which should provide information about the grazing angle dependence of the scattering. A complication arises in determining the scattering strength in non-uniform environments, since the reverberation comes from all azimuths, and since the source and vertical array receivers were not co-located. In such bistatic geometry, the energy arriving at any instant comes from different ranges, azimuths, and vertical angles. However, if the source and receiver are close together, at longer times the geometry approximates the simpler monostatic situation. To help interpretation, results are compared with predictions from a range-dependent bistatic reverberation model. [Work supported by ONR, Ocean Acoustics.]

Shallow-water acoustic experiment in the Strait of Sicily Area: Preliminary results

Shallow-water acoustic and geoacoustic measurements were made in the southwest margin of the Adventure Bank area of the Strait of Sicily in a region having about 120-m water depth and a generally smooth calcareous sand seafloor. Concurrent propagation and reverberation experiments were conducted using horizontal and vertical array receivers with both broadband explosive and controlled narrow-band sources. Propagation is frequency dependent with minimum transmission loss at long range occurring in the frequency band 200–800 Hz. Overall reverberation envelope of duration was about 60 s and includes both diffuse returns and arrivals from major bathymetric features. [Work supported by ONR.]