Browsing Reprints by Title

Now showing items 457-476 of 548

    • 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 ...

    • Stochastic methods of sound-field computation 

      Goodman, Ralph R. (NATO. SACLANTCEN, 1975/10)

    • Sub-bands beam-space adaptive beamformer for port-starboard rejection in triplet sonar arrays 

      Stinco, Pietro; Tesei, Alessandra; Maguer, Alain; Ferraioli, Fabrizio; Latini, Valerio; Pesa, Luca (CMRE, 2019/05)
      This paper addresses the problem of Port-Starboard (PS) beamforming for low-frequency active sonar (LFAS) with a triplet receiver array. The paper presents a new algorithm for sub-bands beam-space adaptive beamforming with ...

    • Subcritical penetration of narrow Gaussian beams into sediments 

      Jensen, Finn B.; Schmidt, Henrik (NATO. SACLANTCEN, 1988/03)
      Complete wave-theory solutions have been obtained numerically for both the reflected and the transmitted fields associated with a narrow Gaussian beam incident on a water-sediment interface near the critical grazing angle. ...

    • Summary and recommendations 

      Clarke, Richard H. (NATO. SACLANTCEN, 1971/12)
      An unfortunate first impression might be that ray tracing is dull, simply because the idea is a very old one. In fact, ray tracing is the single most powerful method available to us for understanding the complexities of ...

    • Supporting AUV localisation through next generation underwater acoustic networks: results from the field 

      Munafó, Andrea; Furfaro, Thomas C.; Ferri, Gabriele; Alves, João (CMRE, 2017/11)
      This work describes how the localisation of autonomous underwater vehicles can be supported through net-worked acoustic communication. The localisation approach in-cludes timing information within acoustic messages to ...

    • Surface duct propagation loss measurements and model predictions at low and mid frequencies 

      Klingbeil, Delia H. (NATO. SACLANTCEN, 1993/08)
      Side-by-side measurements of low- and mid-frequency propagation loss were obtained during a sea test conducted in the North Atlantic during February of 1992. These measurements are compared to each other and with model ...

    • Surface wave spectra 

      Crowther, P. A. (NATO. SACLANTCEN, 1975/10)
      A classification is made of the different types of wave elevation spectra namely lD time spectra, lD spatial spectra, 2D spatial spectra and 3D space-time spectra. Relations with simple single parameter measures of surface ...

    • Swath bathymetry and SAS autofocus using a Chirp source 

      Shippey, Geoffrey; Kröling, Olle (NATO. SACLANTCEN, 1997)
      Swath bathymetry and SAS autofocus can both be treated as problems in correlating echoes from a scatterer distribution on the seabed. Using a chirp source, the phase derived from quadrature match-filtering can replace the ...

    • System functional migration: high-level language to hardware 

      Wu, Y. S.; Lloyd, G. R. (NATO. SACLANTCEN, 1979/12)
      This paper intends to examine system functional allocation among available processing resources in a systematic way. The discussion will focus first on the criteria for assigning functions to processors, that is, horizontal ...

    • Tactical data acquisition experiences 

      Messere, E. L. (NATO. SACLANTCEN, 1972/05)
      The requirements of Tactical Data Acquisition systems are discussed and summarized. Experiences with equipment and their utilization are described including : quantities measured, input signal conditioning, analogue ...