Browsing by Type "Papers and Articles"
Now showing items 41-60 of 562
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A towed CTD chain for two-dimensional high resolution hydrography
(NATO. SACLANTCEN, 1997/04)The need for accurate two-dimensional datasets of temperature and salinity in the upper ocean led to the development of a new type of towed chain. Low-cost sensors are moulded in fins and may be randomly placed on the tow ... -
A unified model for seabed volume and roughness scattering
(NATO. SACLANTCEN, 1997)Seabed scattering is considered taking into account perturbations of different type: volume inhomogeneities and roughness of the interfaces. A description is given in terms of plane waves. The first-order perturbation ... -
A versatile signal-processing system for producing the angular and frequency distribution of acoustic energy in real time
(NATO. SACLANTCEN, 1979/12)For a number of years the US Naval Research Laboratory (NRL) has been conducting a research program in underwater sound propagation using large aperture hydrophone arrays. This research requires the spectral and angular ... -
A wave-theoretic method for estimating the effects of internal tides on acoustic wave transmission
(NATO. SACLANTCEN, 1975/10)The effect of the first mode semidiurnal internal tide on a ducttype sound speed profile was approximated by varying the minimum velocity of the parabolic profile in a sinusoidal fashion with a period of 12.42 hours. The ... -
About the effective Doppler sensitivity of certain nonlinear chirp signals (NLFM)
(NATO. SACLANTCEN, 1993/08) -
Achievable signal gains for line arrays in shallow water
(NATO. SACLANTCEN, 1993/08)The well-documented conformance of signal gain to a 20 log n relationship for deep water, refracted paths, does not apply to shallow water where angular spreading effects from boundary roughness limit the signal gains that ... -
Acoustic ambient noise in the Barents Sea
(NATO. SACLANTCEN, 1982/06)Recorded observations of acoustic ambient noise in the Western Barents Sea are presented. The observations were made in a position approximately 100 km North of North Cape in Norway, with the hydrophone on the bottom - ... -
Acoustic characterization of a shallow water site
(NATO. SACLANTCEN, 1993/08)Results are presented from an exercise aimed at providing a low frequency active sonar environmental characterization of a specific shallow water site in the Gulf of Mexico. Downward refracting acoustic transmission and ... -
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 ... -
Acoustic effects of internal microstructure
(NATO. SACLANTCEN, 1975/10) -
Acoustic noise models
(NATO. SACLANTCEN, 1975/10)The question of modeling the vertical directionality of ambient noise in the ocean is considered. The problem of converting from a description in terms of directional density function to a description in terms of the ... -
Acoustic propagation models as viewed by the sonar systems designer
(NATO. SACLANTCEN, 1971/12)The purpose of this paper is to consider the efforts performed in the development of ray acoustic propagation analyses from the viewpoint of advanced sonar system design. In particular, those parameters required of such ... -
Acoustic propagation through oceanic fronts
(NATO. SACLANTCEN, 1971/12)A resume was given of recent experiments in the Mediterranean, East of Malta, designed as a preliminary test of the effect of oceanic fronts on acoustic propagation. It was apparent that in certain circumstances the ... -
Acoustic properties of the sea floor: a review
(NATO. SACLANTCEN, 1975/10) -
Acoustic scattering from rough surfaces
(NATO. SACLANTCEN, 1975/10)A review of scattering from the ocean bottom and ocean ice cover is given. Areas of deficiency are cited. -
Acoustic scintillations of acoustic waves
(NATO. SACLANTCEN, 1975/10) -
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 ... -
Acoustic source characteristics of merchant ships
(NATO. SACLANTCEN, 1982/06)Merchant ships are sources of broadband acoustic noise which can interfere with and confuse ocean surveillance. The purpose of this discussion is to review: the status of research on and measurements of merchant ship ... -
Acoustical characteristics of the sea floor: experimental techniques and some examples from the Mediterranean Sea
(NATO. SACLANTCEN, 1974/11)The acoustical properties of the sea floor are primarily determined by the physical properties of the sediments, layering in the sediments, and the roughness of the bottom and sub-bottom. Over the last decade many cores ... -
Acoustical probing for microbubbles at sea
(NATO. SACLANTCEN, 1975/10)Free gas bubbles have been indicted for many physical processes at sea including: scavenging detritus and chemicals from the ocean volume; generating droplets whose salts affect thunderstorm activity over the sea; providing ...