Browsing Reprints by Subject "Underwater acoustics"
Now showing items 1-20 of 46
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A relation between multipath group velocity, mode number, and ray cycle distance
(CMRE, 2014/01)Weston's ray invariant or "characteristic time" in a range-dependent environment is exactly equivalent to the Wentzel-Kramers-Brillouin phase integral for ducted normal modes. By considering a ray element it is shown that ... -
A review of oceanic fronts
(NATO. SACLANTCEN, 1975/10)This paper will start with a brief account of oceanic frontal research. The definition of oceanic and acoustic fronts and the distinction between them will be discussed. Examples of frontal structure dynamics, correlation ... -
A solution of of the wave sound equation in shallow water for real speed profiles and solid bottom under sediment
(NATO. SACLANTCEN, 1975/10)The wave equation has been solved by using normal mode theory. The medium is assumed to be horizontally stratified. A closed form solution has been found in the case of GANS - PEDERSEN types of density and sound-speed ... -
A survey of practical considerations relative to the processing and analysis of underwater acoustic signals
(NATO. SACLANTCEN, 1972/05)An investigation, aimed at bringing into sharper focus · tb~ strong interrelationships that exist between the measurement, p r o c essing, and analysis of underwater acoustic signals, is conducted. Emphasis is on practical ... -
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 properties of the sea floor: a review
(NATO. SACLANTCEN, 1975/10) -
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 ... -
Beam spreading and loss of spatial coherence in an inhomogeneous and fluctuating ocean
(NATO. SACLANTCEN, 1975/10)A theory has been developed that enables estimates to be made of beam bending, beam spreading and loss of spatial coherence. In this paper we concentrate on the loss of spatial coherence due to scattering. Using a minus ... -
Calculation of reverberation and average intensity of broadband acoustic signals in the ocean by means of the RAIBAC computer model
(NATO. SACLANTCEN, 1976/04)Based on the conventional ray-tracing principle, a fast numerical algorithm is developed that calculates averaged propagation loss and reverberation of underwater sound. The averaging is performed by summing incoherently ... -
Comparison of CONGRATS ray tracing predictions with MEDUSA measurements of reverberation
(NATO. SACLANTCEN, 1971/12)From the user's point of view, ray tracing is just a computer procedure which is inserted into larger programs of different degrees of complexity . The following table indicates in which kind of programs this procedure is ... -
Considerations relating to the calculation of sound velocity
(NATO. SACLANTCEN, 1971/12) -
Digital acoustical processing at Woods Hole Oceanographic Institution
(NATO. SACLANTCEN, 1972/05) -
Doppler passive fathometry
(CMRE, 2019/05)Passive fathometry is a technique whereby broadband ambient ocean noise received on an array of hydrophones is averaged and cross-correlated to produce a sub-bottom profile [Siderius, Harrison, and Porter (2006). J. Acoust. ... -
Effects of sea-ice ridges on sound propagation in the Arctic Ocean
(NATO. SACLANTCEN, 1975/10)An environmental/acoustic model of sound propagation in the Arctic Ocean, which accounts for reflection losses from ridged sea ice, has been developed. In this model sea-ice ridges are represented as infinitely long, ... -
Experimental data on the refraction of underwater explosion pulses
(NATO. SACLANTCEN, 1971/12)There are several reasons why a researcher in underwater acoustics might be interested in the use of explosion pulses as sources. The most generally recognized reason is that explosions are convenient and powerful sources ... -
Gas bubbles in the sea: a review and model proposals
(NATO. SACLANTCEN, 1975/10)The literature pertaining to both free bubbles (pt 1) and bubbles associated with fish anotomy (pt 2) is reviewed with particular emphasis on their distributions in the sea and influencing factors. An attempt is made to ... -
Geometrical properties of underwater sound propagation
(NATO. SACLANTCEN, 1971/12) -
Hamiltonian methods in hydro-acoustic propagation
(NATO. SACLANTCEN, 1971/12)The investigation that I wish to outline here originated in the military need of forecasting detection p r obabilities of underwater acoustic emitters, in case s in which only a somewhat general idea of the sound speed ...