Browsing Reprints by Title

Now showing items 447-466 of 548

    • Some acoustic effects of internal macrostructure 

      Mellen, Robert H.; Browning, David G. (NATO. SACLANTCEN, 1975/10)
      Some recent experimental developments relating to internal oceanographic- acoustic interactions are reviewed. Besides amplitude and phase fluctuations, a major concern is scattering into shadow regions. Associated oceanographic ...

    • Some comments on ray theory with examples from current NUC ray trace models 

      Bucker, H. P. (NATO. SACLANTCEN, 1971/12)
      Three topics were covered in this paper: 1. Ray Sweep-out Method - a technique for calculating sound intensities at a large number of receiver points in range and depth . 2. Bi-static Reverberation Model - a technique based ...

    • Some effects of large-scale oceanography on acoustic propagation 

      Guthrie, A. N.; Shaffer, John D.; Fitzgerald, R. M. (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 ...

    • Some high efficiency digital signal processing techniques for high speed signal processing systems 

      Cappellini, Vito (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 ...

    • Some near-field acoustic imaging techniques in noise ranging 

      Rafine, B.; Elias, G. (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 ...

    • Some ray and intensity solutions in the complex plane 

      Krol, Hans R. (NATO. SACLANTCEN, 1974/02)
      This paper presents a method to test range-dependent ray-tracing programs. The method is based on complex-function theory. From an analytic function that has a zero point at the emitter, expressions for sound speed, ray ...

    • Some statistical characteristics of ocean motions from current measurements 

      Gonella, J. A. (NATO. SACLANTCEN, 1972/09)
      A rotary-component method for analysing vector series in two dimensions was developed for the study of the coupling between wind-stress and surface current [Gonella, 1972J. This method provides a good tool for instrumental ...

    • Sonar beam-forming with an array processor in real time 

      Wagner, Walter G. (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 ...

    • Sound absorption by suspended particulate matter 

      Brown, N. R.; Leighton, Timothy Grant; Richards, S. D.; Heathershaw, A. D. (NATO. SACLANTCEN, 1997)
      A series of experiments has been performed to study the viscous absorption of sound by particulate suspensions typical of those found in coastal waters. The effect due to the particles in the frequency range of 50 - 150 ...

    • Sound propagation in a wedge-shaped ocean with a penetrable bottom 

      Jensen, Finn B.; Kuperman, William A. (NATO. SACLANTCEN, 1980/07)
      Modal cutoff during up-slope propagation in a wedge-shaped ocean is studied using the parabolic equation model; theoretical results are compared with some model tank experiments.

    • Sound propagation in shallow water: a detailed description of the acoustic field close to surface and bottom 

      Jensen, Finn B. (NATO. SACLANTCEN, 1982/02)
      Experimental data are compared with normal-mode predictions for an isovelocity shallow-water propagation channel overlying a complicated layered bottom. Measurements were made close to both the sea surface and the sea floor ...

    • Source and receiver responses in boreholes 

      Hovem, Jens M.; Lotsberg, Oddvar (NATO. SACLANTCEN, 1997)
      This report considers the acoustic interaction between the acoustic freld rn a borehole and the elastic field in the surrounding formation. The problem with acoustic-seismic radration of energy from a source in a fluid ...

    • Source localization for a low frequency active multistatic sonar system 

      Hughes, E. S. (NATO. SACLANTCEN, 1993/08)
      In a low frequency active bistatic or multistatic sonar system, it is essential tohave accurate knowledge of the location of the transmitting source ship. Inaccuracies inthis information translate directly to errors in the ...

    • Spatial and temporal coherence in a long range, upslope environment 

      DeDominicis, Theresa S.; Kooij, Theo (NATO. SACLANTCEN, 1993/08)
      In an active acoustic test conducted off the USA Pacific Coast in November-December 1991, a low-frequency source, kept stationary over the deep basin, insonified from long range the coastal slope and shelf. An autonomous, ...

    • Spatial correlation of surface-generated noise in a stratified ocean 

      Kuperman, William A.; Ingenito, Frank (NATO. SACLANTCEN, 1980/10)
      A model is developed for the calculation of the spatial properties of the noise field produced in a stratified ocean by the action of wind at the surface. The random noise sources are represented by correlated monopoles ...

    • Spatial variability of surficial shallow water sediment geoacoustic properties 

      Richardson, Michael D. (NATO. SACLANTCEN, 1986/06)
      Variability of surficial sediment geoacoustic properties was determined from cores collected at eight shallow-water continental shelf regions in the U.S., Italy and Australia. Highly porous muds found in low energy ...

    • Special formulation of modified ray analysis for machine computation 

      Murphy, Edward; Davis, J. A. (NATO. SACLANTCEN, 1971/12)

    • Statistical characterization of shallow-water bistatic sonar reverberation and noise 

      Pack, Kenneth D.; Turner, Michael V.; Ling, James M.; Monti, Joseph M. (NATO. SACLANTCEN, 1993/08)
      Shallow-water, low-frequency bistatic sonar measurements often exhibit high noise caused by bathymetric reverberation and other sources. Understanding the noise statistics is an essential first step in developing filters ...

    • Statistical evaluation of 80 kHz shallow-water seafloor reverberation 

      Lyons, Anthony P.; Abraham, Douglas A.; Akal, Tuncay; Guerrini, Piero (NATO. SACLANTCEN, 1997)
      In this work a comparison is presented between 80 kHz reverberation statistics obtained at shallow water sites around Sardinia and Sicily. The data include measurements from several distinct bottom provinces, including ...

    • Status of ray theory development of Naval Undersea Research and Development Center 

      Gordon, D. F. (NATO. SACLANTCEN, 1971/12)
      The first part of this paper discusses NUC (Naval Undersea Research and Development Center) work on the accuracy and validity of ray theory. By comparing the range to convergence zones as indicated by experiment and by ...