Browsing Reprints by Subject "High Frequency Acoustics"
Now showing items 1-20 of 25
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A high frequency approach for seabed vegetation characterization
(NATO. SACLANTCEN, 1997)This paper focuses on the characterization of seabed vegetation, an interesting problem in a lot of Mediterranean sea coastal sites since water quality and pollution degree can be efficaciously solved by investigating the ... -
A noise directionality model including variable bathymetry
(NATO. SACLANTCEN, 1997)In this paper we investigate the noise directionality due to distributed surface sources m several envtronments with a uniformly sloping sea bed. Of particular interest are frequency dependence and the question of the ... -
Analysis and problems of HF acoustic coherent and incoherent simulations in shallow water
(NATO. SACLANTCEN, 1997)Shallow water environments create complex scattering condit~ons due to the sea surface and bottom scattering mechanisms. An analysis of the effects of the scattering mechan~smso n sonar images of simple targets in shallow ... -
Determination of velocity profile and sea bed characteristics from high frequency pulse propagation in a shallow water Mediterranean environment
(NATO. SACLANTCEN, 1997)Time-domain features of shallow water Mediterranean and Yellow Sea data are simulated for frequency band widths of 0.8 kHz with a centralfrequency of 3.2 kHz. Contour plots of pulse arrivals in time and depth are analyzed ... -
Dynamic attenuation extraction of seafloor sediments from very high resolution acoustic data
(NATO. SACLANTCEN, 1997)An approach to acquire geophysical information of seabed sediments as derrved from acoustic attenuation rs described. Using thefrequencies corresponding to the signal power spectrum maximum and a point 3 dB below, signal ... -
Effects of sea bed structure on high frequency acoustic reverberation in shallow water
(NATO. SACLANTCEN, 1997)Although undoubtedly sea bed structures, patterns, and composition affect the reverberation of high-frequency acoustic energy, the extent of their influence is not well known. The effects of varying selected bedform ... -
Geoacoustic modeling of the seabed at higher frequencies
(NATO. SACLANTCEN, 1997)In propagation at higher frequencies, local fluid motion in "hidden coordinate" systems and local discontinuities due to gas bubbles and bioturbation have a perturbing effect on the wave field. To model these effects, a ... -
High frequency acoustic observations of Mediterranean flow into the Black Sea
(NATO. SACLANTCEN, 1997)The physical behavior of Mediterranean flow entering the Black Sea through the Strat of Istanbul is described using a variety of high frequency acoustic systems. Because of the density difference between salty Meditermnean ... -
High frequency acoustic propagation in coastal waters
(NATO. SACLANTCEN, 1997)High Frequency Acoustic Propagation experiments were performed with bottom-mounted sources and receivers at different coastal sites. A measurement technique has been developed and propagation loss data have been taken using ... -
High frequency matched field processing
(NATO. SACLANTCEN, 1997)Results are discussed from a high frequency (0 9-5 7 kHz), very shallow water (<10 m) experiment exploring the feasibility of carrying out matched field processing in this frequency and water depth regime The data was ... -
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 ... -
High-frequency normal-mode calculations in deep water
(NATO. SACLANTCEN, 1982/10)A method has been developed to perform high-frequency deep-water normal-mode calculations in the multikilohertz region in water depths of the order of 5 km. The results from this technique agree with fast field program ... -
Measurement and interpretation of angular spreading from multiple boundary interactions in a shallow water channel
(NATO. SACLANTCEN, 1997)The problem of angular spreading of sound that has undergone multiple boundary scattering (both sea surface and sea bed) in a shallow water channel is discussed. Measurements made of the horizontal spatial coherence along ... -
Measurements and modelling of high-frequency acoustic scattering by a rough seafloor and sea surface
(NURC, 2009/12)Acoustic scattering by a rough, possibly dynamic interface is experimentally studied by insonifying the seabed and the sea surface at high frequency at various incidentangles. A directional source working at 300 kHz was ... -
Modeling of subcritical penetration into sediments due to interface roughness
(NATO. SACLANTCEN, 1997)Recent experimental results reveal acoustic penetration into sandy sediments at grazing angles below the critical angle. We have been investigating a mechanism for subcritical penetration based on scattering at a rough ... -
Modeling range-dependent, high-frequency, shallow-water torpedo reverberation data
(NATO. SACLANTCEN, 1997)The high-frequency, forward bottom losses predicted by a lossy Rayleigh and a Biot poroelastic sediment model are substantially different. These differences will accumulate and become measurable in multiple bottom bounce ... -
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 ... -
Seabed characterization by inversion of parametric sonar data: selection of the cost function
(NATO. SACLANTCEN, 1997)A class of possible cost functions to be used in model-based estimation of bottom parameters from highfrequency backscatter signals is introduced. The cost is based on the properttes of the signal in the wavelettransformed ... -
Small scale volumetric inhomogeneities of shallow water sediments: measurements and discussion
(NATO. SACLANTCEN, 1997)There is a consensus that high-frequency acoustic scattering by the ocean bottom is partly due to sediment volumetric inhomogeneities, r e., random fluctuations in sediment sound speed and density. Understanding the spatial ... -
Temporal modeling of high frequency (30-100 kHz) acoustic seafloor backscatter: shallow water results
(NATO. SACLANTCEN, 1997)A temporal model of high frequency seafloor acoustic backscatter is presented and compared to recorded echoes from terrigenous sediments. Using acoustic properties correlated with mean grain size, the echo shapes and ...