CMRE Open Library: Recent submissions
Now showing items 801-820 of 882
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Notes on the interpretation of ambient noise statistics
(NATO. SACLANTCEN, 1982/06)Interpretation of statements about the character of ambient sea noise, as well as schemes to measure or model noise, are sensitive to the context or underlying view of what is essentially a stochastic process. A framework ... -
Underwater ambient noise: proceedings of a conference held at SACLANTCEN on 11-14 May 1982, vol. 2 - Unclassified Papers, part 2
(NATO. SACLANTCEN, 1982/06)Contents: PROCESSING TECHNIQUES--A method of estimating the influence of ship's noise on ambient noise measurements; Optimal detection and tracking of acoustical noise sources in a time-varying environment; Influence of ... -
Ambient noise levels in the Northeast Pacific ocean as measured by aircraft-dropped sonobuoys
(NATO. SACLANTCEN, 1982/06)Ambient noise measurements obtained from sonobuoys air-dropped by U.S.Navy P-3 aircraft during operations over the northeastern Pacific Ocean from January 1978 to December 1980 have been analysed for spatial and temporal ... -
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 - ... -
Depth dependence of directionality of ambient noise in the North Pacific: experimental data and equipment design
(NATO. SACLANTCEN, 1982/06)Ambient ocean noise studies have been part of the research program of the Marine Physical Lab (MPL) for many years. In recent years this work has included several studies of the depth dependence of vertical directionality ... -
A real time system for towed array calibration and performance analysis, or how to get 50 dB sidelobes from a towed array
(NATO. SACLANTCEN, 1982/06)Sidelobe suppression levels of 30 dB for a towed array are generally considered excellent; values above that are considered exceptional or unachievable. However, 40 t o 50 dB suppression levels have been achieved and ... -
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 ... -
Seismic and hydroacoustic sensing of infrasonic noise in coastal waters
(NATO. SACLANTCEN, 1982/06)Three-component ocean-bottom seismometers with radio links have been deployed in coastal waters to investigate natural and man-made noise at extremely low frequencies. Seismograms from one or up to three sensor stations ... -
Low-frequency seismic and hydroacustic noise measurements in a fjord
(NATO. SACLANTCEN, 1982/06)Low frequency ambient noise signals from an ocean bottom seismometer (oBS) put on the sea floor of a Norwegian fjord have been studied. The instrument contains 3 seismometers and one hydrophone, and signals from all 4 ... -
Arctic ambient noise statistical measurement results and their implications to sonar performance improvements
(NATO. SACLANTCEN, 1982/06)Recent analyses of FRAM II arctic data have shown that under ice ambient noise can be at times highly impulsive and non-Gaussian. The analyses included time domain statistical measurements which were consistent with ... -
Le programme Ulysse: réseau de bouées pour l'étude statistique du bruit ambiant sous-marin
(NATO. SACLANTCEN, 1982/06) -
Flow noise interference in measurements of infrasonic ambient noise
(NATO. SACLANTCEN, 1982/06)Estimates are presented of the local noise generated at infrasonic frequencies by turbulent water flowing in the vicinity of hydrophones used for measurements of ambient noise in the sea. Three situations are discussed: a ... -
Role of propagation in ambient noise
(NATO. SACLANTCEN, 1982/06)To be useful for modern ASW systems design and analyses, descriptions of ambient noise fields must go beyond average omnidirectional spectra and include horizontal and vertical patterns, fluctuations with time, dependencies ... -
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 ... -
Geometrical properties of underwater sound propagation
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Arrays and array processors: future real time applications in oceanography and sonar
(NATO. SACLANTCEN, 1979/12)In the last several years oceanographic applications of arrays have increased substantially. The spatial resolution and redundancy provided by arrays have been necessary in the interpretation of signal propagation in complex ... -
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 ... -
An introduction to adaptive array processing
(NATO. SACLANTCEN, 1979/12)Array processing systems which can respond to an unknown interference environment are currently of considerable interest. The fundamentals of such systems are by no means new - basically they depend on Weiner's filter ... -
Sonar beam-forming with an array processor in real time
(NATO. SACLANTCEN, 1979/12)A real-time sonar beam-forming system is described which consists of a minicomputer as host computer and an array processor. Beam-forming is accomplished by using the FFT algorithm in the processor. The system is also ...