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Now showing items 161-180 of 882
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Theory of scattering and reflection of sound from the sea surface
(NATO. SACLANTCEN, 1975/10)Theoretical work on scattering and reflection of sound from the random timevarying rough sea surface is critically reviewed. It is shown that sound scattering from the sea surface may be treated as a purely acoustic boundary ... -
Underwater acoustics - modelling: keynote address
(NATO. SACLANTCEN, 1975/10) -
Highlights of bottom topography inferred from received depression and bearing angles
(NATO. SACLANTCEN, 1975/10)Statistical properties of the acoustic reflection from the ocean floor have been studied for a var i.ety of bottom types including deep, smooth, flat topography thorough, jagged bottom in shallower (~l km) depths. Explosive ... -
Some effects of large-scale oceanography on acoustic propagation
(NATO. SACLANTCEN, 1975/10)A propagation experiment was conducted along a great circle track in the North American Basin, beginning at a point 400 km north of Antigua, W.I. and ending at the Grand Banks of Newfoundland. Shallow explosive sources ... -
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 ... -
Refraction of sound in the sea floor
(NATO. SACLANTCEN, 1975/10)A major mode of propagation of acoustic energy at low frequencies is a shallow refracted path through unconsolidated sediments of the sea floor. Successful modelling of the bottom-refracted mode of propagation requires ... -
A theoretical model for doppler spread of backscattered sound from a composite roughness sea surface
(NATO. SACLANTCEN, 1975/10)For calculating the Doppler spread of acoustical reverberation from the sea surface, good results are achieved by applying a composite-roughness model. The small wavelets primarily responsible for the backscattering are ... -
Ocean-bottom reflectivity (a point of view)
(NATO. SACLANTCEN, 1975/10)The analysis procedures for extracting bottom loss values from pulsed acoustic signals that have interacted with the ocean bottom do not inherently consider sub-bottom refraction and reflection of sound, which are important ... -
Reflection of sound from a layered ocean bottom
(NATO. SACLANTCEN, 1975/10) -
Acoustic effects of internal microstructure
(NATO. SACLANTCEN, 1975/10) -
Intensity-range relations for shallow-water sound propagation
(NATO. SACLANTCEN, 1976/04)Convincing experimental evidence is presented to show that various "decay laws" for the decrease of sound intensity with increasing range can give high-quality representation for shallow water data. However, while a sequence ... -
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 ... -
The steady state of the step structure in the Tyrrhenian Sea
(NATO. SACLANTCEN, 1978/10)A deep step structure, in which mixed layers alternate with high gradient interfaces, is a characteristic feature of the Tyrrhenian Sea. Three oceanographic cruises (May 1972, May 1973 and October 1974), supported by the ... -
Model for the frequency spread of backscattered underwater sound based on the facet model of the rough sea surface
(NATO. SACLANTCEN, 1978/11)A theoretical model for the doppler spread of backscattered acoustic waves from the rough sea surface is described on the basis of the decomposition of the continuous sea-surface spectrum that leads to the concept of facets. ... -
Two-dimensional space-series analysis for sea-floor roughness
(NATO. SACLANTCEN, 1979/10)For a quantitative description of the sea-floor roughness, a numerical method has been developed to obtain the two-dimensional power spectrum and the autocorrelation function. The determination of these parameters gives ... -
The MPS-3 and the SPS-81
(NATO. SACLANTCEN, 1979/12)The Larqe Aperture Acoustics Branch of the Naval Research Laboratory has developed a sea-qoinq signal processinq system in which two different types of array processors are used - a Signal Processing Systems SPS-81 and ... -
Some high efficiency digital signal processing techniques for high speed signal processing systems
(NATO. SACLANTCEN, 1979/12)Some high efficiency digital signal processing techniques, based on digital filtering are presented for real-time general-purpose, high-speed signal processing systems. At first high efficiency one-dimensional and ... -
Overview of the ADPS signal processor
(NATO. SACLANTCEN, 1979/12) -
Laboratory utilization of a standard signal processor
(NATO. SACLANTCEN, 1979/12)The AN/UYS-l Advanced Signal Processor (ASP), or PROTEUS, is the U.S. Navy's standard signal processor and is being utilized in several systems. For shipboard use, the ASP is used as a processor with no peripherals, generally ... -
Development of military ARGUS computers and MOD bus for close-coupled signal processing applications
(NATO. SACLANTCEN, 1979/12)The next generation of Naval sonar systems will make extensive use of flexible programable modules to implement signal-processing algorithms. A number of UK Defence Establishments are engaged in a series of coordinated ...