Reprints: Recent submissions
Now showing items 301-320 of 548
-
Digital acoustical processing at Woods Hole Oceanographic Institution
(NATO. SACLANTCEN, 1972/05) -
Obtaining the ocean index of refraction spectrum from the acoustic amplitude fluctuations
(NATO. SACLANTCEN, 1997)The feasibility of using acoustic measurements to determine the properties of a shallow water internal wave field is investigated through numerical simulations. The random intemal wave field is modeled by a generalized ... -
Attenuation of shear waves in near-surface sediments
(NATO. SACLANTCEN, 1997)In situ measurement of compressional and shear speed and compressional attenuation in near-surface marine sediments is a well-developed technology but techniques required to measure shear attenuation have lagged behind. ... -
An experimental investigation of the contribution of sediment volume scattering to acoustic backscatter measured in the shallow waters of the Florida Strait
(NATO. SACLANTCEN, 1997)Experiments were conducted in the Florida Strait region of the United States in July 1995 for the purpose of investigating the contribution of sediment volume scattering to measured backscatter levels at frequencies between ... -
Acoustic signal dispersion and distortion by shallow undersea transmission channels
(NATO. SACLANTCEN, 1997)The undersea littoral is an adverse medium for acoustic signal transmission to horizontal ranges of many water depths. Reflections and scattering in the bounded, nonhomogeneous channel disperse the arrivaj of received ... -
A new ambient noise imaging system for ANI, passive and bistatic active acoustic imaging in shallow water
(NATO. SACLANTCEN, 1997)Shallow water active and passive sonars can be usefully complimented by broadband Ambient Noise Imaging (ANI) systems. The first AN1 system was largely analogue, produced good images at 38 m range, but was bulky and permitted ... -
Autofocusing a synthetic aperture sonar using the temporal and spatial coherence of seafloor reverberation
(NATO. SACLANTCEN, 1997)An autofocusing algorithm for the compensation of translational motion errors of a sea floor rmaging synthetic aperture side scan sonar is presented. The algorithm does not depend on the presence or absence of dominant ... -
High-resolution characterization of seafloor sediments for modeling acoustic backscatter
(NATO. SACLANTCEN, 1997)Quantitative information on fine-scale sediment inhomogeneity is extremely scarce and sorely needed for developing realistic volume scattering models. To address this deficiency, we present a novel approach for sediment ... -
The SACLANTCEN interactive time series analysis system
(NATO. SACLANTCEN, 1972/05)The purpose of this paper is to describe the new conversational signal processing system which is being developed by the Computer Section at SACLANTCEN. This system, which i ncludes input/ output devices, can be used alone ... -
Riverine environmental acoustics at an ocean estuary
(NATO. SACLANTCEN, 1997)The purpose of these studies was to investigate some of the more important geoacoustrc parameters that might govern the use of high frequency sonar in muddy rivers, where they flow into the sea. Both environmental and ... -
Shallow water propagation incorporating both bubble plumes and sea-surface roughness
(NATO. SACLANTCEN, 1997)The effect of including a range dependent bubble layer and a suitable sea surface spectrum in modeling shallow water propagation is analyzed. Propagation is simulated through a hrghly accurate model based on a modified PE ... -
Terrain mapping with forward looking sonar on unmanned underwater vehicles
(NATO. SACLANTCEN, 1997)In the future, successful reconnaissance operations conducted in shallow water with Autonomous Underwater Vehicles will rely heavily on a high performance, high resolution, forward look sonar coupled with terrain mapping ... -
Seabed survey by VHR multichannel seismics: GEOSIS project
(NATO. SACLANTCEN, 1997)Site surveys prior to the installation of offshore facilities are required to obtain shallow soil structural and geotechnical information. The French project GEOSIS was aimed at improving both geophysical and geotechnical ... -
Comments on the ray theory approximation
(NATO. SACLANTCEN, 1971/12) -
Acoustic characterization of submerged aquatic vegetation
(NATO. SACLANTCEN, 1997)The acoustic characteristics of submerged aquatic vegetation (SAV) were investigated in order to enhance the performance of mine-hunting and weapon sonars in littoral reglons. The specres of seagrass initially studied was ... -
Interactive tools for the exploration and analysis of multibeam and other seafloor acoustic data
(NATO. SACLANTCEN, 1997)The Ocean Mapping Group has developed a full suite of software tools for the real-time or near real-time display, editing, quality control, interpretation and visualization of multibeam sonar data. The combination of ... -
Estimating surface orientation from sonar images
(NATO. SACLANTCEN, 1997)A maximum likelihood method for estimating remote surface orientation from multi-static sonar images is presented. It is assumed that the sonar images are corrupted by signal-dependent noise, known as speckle, arising from ... -
High resolution feature extraction from reverberation data
(NATO. SACLANTCEN, 1997)A new method of signal approximatzon is presented which has the capability to model complex active returns due to reverberation. The method explored herein is data adaptive in the sense that high resolution processing is ... -
Estimation of chirp sonar signal attenuation for classification of marine sediments: improved spectral ratio method
(NATO. SACLANTCEN, 1997)Remote sediment classification through acoustic methods is of great interest for a few years. The attenuation coefficient of the transmitted wave is an important feature to characterize physical sediment layers properties. ...