Browsing CMRE Publications by Issue Date
Now showing items 261-280 of 882
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Some near-field acoustic imaging techniques in noise ranging
(NATO. SACLANTCEN, 1985/01)Acoustical imaging of ship radiating noise sources requires the developrnent of near field array processing. Performance analysis of a linear processing with static sources together with its adaptation to moving sources ... -
Temporal and spatial variabilities in shallow water acoustics: measurements and predictions
(NATO. SACLANTCEN, 1985/03)An acoustic signal propagating in the sea is generally degraded not only by interactions with the bottom and surface boundaries, but also by volume inhomogeneities caused by non-uniformities in temperature, density, and ... -
Deep-sea circulation in the Alboran sea
(NATO. SACLANTCEN, 1985/04)Alboran Sea circulation between 220 and 1100 m depth is studied. Interaction between three types of water masses in this area causes a complicated flow pattern. Atlantic water flowing as a jet through the Strait of Gibraltar ... -
Underwater photography for quantitative description of bottom roughness
(NATO. SACLANTCEN, 1985/04)Knowledge of the roughness of the sea floor is obviously of great importance in marine geology for understanding the processes of the ocean bottom, and in underwater acoustics for understanding the scattering process. The ... -
Multiple beamforming
(NATO. SACLANTCEN, 1985/07)Beamforming techniques are generally based on the assumption that the received signal arrives from -
The influence of fluctuations in acoustic travel time on locating the position of an underwater sound source
(NATO. SACLANTCEN, 1985/10)This paper investigates the accuracy of an underwater acoustic positioning system in locating a sound source that transmits at unknown times in conditions in which the acoustic travel times between -
A microcomputer-controlled digital acquisition and analysis system for the expendable bathythermograph
(NATO. SACLANTCEN, 1985/10)For a number of years the expendable bathythermograph (XBT) has been an important tool for basic and applied oceanographic survey work. This has led to a significant body of work being done on the accuracy of the XBT system ... -
The determination of permeability in in-situ marine-floor sediments
(NATO. SACLANTCEN, 1985/11)A method of evaluating in situ permeability of unconsolidated marine floor sediments has been -
A fast field model for three-dimensional wave propagation in stratified environments based on the global matrix method
(NATO. SACLANTCEN, 1986/03)A three-dimensional fast field program (FFP) model based on the global matrix method will be presented. Compared to traditional propagator matrix methods, the global matrix method allows for a more efficient, and, furthermore, ... -
Efficient global matrix approach to the computation of synthetic seismograms
(NATO. SACLANTCEN, 1986/05)A numerically efficient global matrix approach to the solution of the wave equation in horizontally stratified environments is presented. The field in each layer is expressed as a superposition of the field produced by the ... -
Medium-induced low-frequency fluctuations in acoustic transmission loss: examples from measurements in selected geographical areas
(NATO. SACLANTCEN, 1986/06)The ocean is a complex, highly variable acoustic nedium. A propagating acoustic signal is affected by a host of phenomena, including the sea-surf ace and bottom, volume inhomogenei ties, internal waves and tides, and ... -
The use of Love waves to determine the geoacoustic properties of marine sediments
(NATO. SACLANTCEN, 1986/06)The importance of the geoacoustic properties of marine sediments for low-frequency shallow water propagation is well established. Reliable compressional properties can be obtained from laboratory analysis of collected ... -
Evaluation of experimental techniques for determining the plane wave reflection coefficient at the sea floor
(NATO. SACLANTCEN, 1986/06)One of the most commonly used techniques for determinati on of the geoacoustical properties of the sea bed is the measurement of plane wave reflection coefficients at the ocean bottom. An incident field is pr oduced by ... -
Directional measurements of low-frequency acoustic backscattering from the seafloor
(NATO. SACLANTCEN, 1986/06)Long-range, low-frequency directional measurements of acoustic backscattering from the seafloor were made in the Tyrrhenian Sea using explosi ve sound sources. The signals were received by a horizontal towed array of ... -
Shear properties of ocean sediments determined from numerical modelling of Scholte wave data
(NATO. SACLANTCEN, 1986/06)Recently it has become apparent that shear properties of ocean sediments are most easily determined from measured propagation characteristics of seismic interface waves. We use a newly developed numeri ca l model of wave ... -
Evaluation of low-frequency bottom backscattering strength vs grazing angle by means of multiple beamforming
(NATO. SACLANTCEN, 1986/06)Bottom backscattering strength was measured in deep water as a function of grazing angle in the Balearic Abyssal Plain of the Mediterranean. The measurements were made with a towed, narrowband low-frequency omnidirectional ... -
Interface wave studies on the Ligurian shelf usingan OBS array: experimental results and propagation models
(NATO. SACLANTCEN, 1986/06)Seismic waves travelling in the water/sediment or subbottom sediment/sediment interface have been the subject of considerable interest in recent years. Experiments have confirmed the existence of interface waves in different ... -
Automatic picture transmission receivers for weather satellite images: a brief introduction and survey of some commercially-available equipment
(NATO. SACLANTCEN, 1986/06)The Automatic Picture Transmission (APT) signal is broadcast from several polar-orbiting weather -
Time dependence of infrasonic ambient seafloor noise on a continental shelf
(NATO. SACLANTCEN, 1986/06)SACLANTCEN is conducting a long term programme of ambient noise measurements that cover the frequency band from 1 to 100 Hz. A sea-bed sensor consisting of three seismometers and a hydrophone has been deployed close to the ...