Reprints: Recent submissions
Now showing items 401-420 of 548
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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 ... -
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 ... -
A theoretical model for the backscattering strength of a composite roughness sea-surface
(NATO. SACLANTCEN, 1974/02)The surface-backscattering strength is calculated according to Rayleigh theory for surface excursions much smaller than the sound wavelength. By taking into account of self-shadowing and modulation of grazing angles, the ... -
Some ray and intensity solutions in the complex plane
(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 ... -
The wave equation in a medium with a time-dependent boundary
(NATO. SACLANTCEN, 1974/02)It is shown that the Helmholtz equation is not exactly correct for a medium with a time-dependent boundary. The equation can be used with very good approximation when the time-derivative of the surface elevation is much ... -
Intensity calculations along a single ray
(NATO. SACLANTCEN, 1974/02)A method is presented for the calculation of sound intensity using only one ray. The sound-velocity profile is assumed to be continuous up to the second derivative and it is supposed that the ray equations are solved ... -
Acoustic propagation models as viewed by the sonar systems designer
(NATO. SACLANTCEN, 1971/12)The purpose of this paper is to consider the efforts performed in the development of ray acoustic propagation analyses from the viewpoint of advanced sonar system design. In particular, those parameters required of such ... -
Some comments on ray theory with examples from current NUC ray trace models
(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 ... -
Application of ray tracing with horizontal gradient to monostatic boundary reverberation
(NATO. SACLANTCEN, 1971/12)Presented is the current work being done at the Naval Research Laboratory (NRL) on the development of a series of computer programs to predict long range, low frequency, monostatic boundary reverberation. The emphasis is ... -
Considerations on numerical and experimental propagation models for two-dimensional variations of medium properties
(NATO. SACLANTCEN, 1971/12)One of the problems the FWG is dealing with is the prediction of sound propagation loss in shallow water. A part of this problem is being treated by bringing measurements and numerical computation into relationship. -
Approximate methods for ray tracing
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Rays and statistical diffraction theory
(NATO. SACLANTCEN, 1971/12)A method of extending ray tracing is proposed, such that mediumscale irregularities of a statistical nature are taken into account along with large-scale irregularities in refractive index of the medium. -
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 ... -
Application of the Riesz potential to the Cauchy problem for wave propagation in an inhomogeneous medium
(NATO. SACLANTCEN, 1971/12)The method of Riesz [Ref. l] for the solution of hyperbolic partial differential equations is applied to the Cauchy problem for the wave equation. It is shown that the first term in the Riesz potential function, which is ... -
The effect of gravity-forced oscillations at the base of the duct on its effective depth as a channel for acoustic rays
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Special formulation of modified ray analysis for machine computation
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Effect of different bandwidths for the detection of extended targets in reverberation
(NATO. SACLANTCEN, 1993/08)In this paper, firstly the theoretical background of bandwidth effects on detection in noise and reverberation is presented in some detail, and secondly the relevant results of sea. trials with a low frequency active sonar ... -
Real time-frequency active sonar processing: a massively parallel approach
(NATO. SACLANTCEN, 1993/08)A paradigm for massively parallel processing of matched filters, replica correlators, ambiguity functions and time-frequency distributions using an SIMD (Single Instruction Multiple Data) programming methodology is presented. ... -
Considerations related to warfare system design and operation of tactical platforms in a low- frequency active sonar environment
(NATO. SACLANTCEN, 1993/08)Low-Frequency Active Sonar System (LFASS) can provide significant improvements in the detection, localization and classification of very quiet submarine contacts. Achievement of the predicted performance improvements will ...