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Date 17-19 Sept. 1979

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Displaying Results 1 - 25 of 153
  • [Front cover and table of contents]

    Publication Year: 1979, Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1979, Page(s): 0
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    Freely Available from IEEE
  • FIR Digital Filters in a Linear Array Processor

    Publication Year: 1979, Page(s):1 - 5
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (246 KB)

    Details of frequency domain beamforming for the processing of a broadband sonar frequency signal from a linear array are presented. The case of a frequency resolution of about 0.025 Hz is employed as an example. The input sampling rate is determined to span the frequency broadband of interest. This is followed by an inphase and quadrature approach to shift a chosen 5 Hz band to the baseband. A cas... View full abstract»

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  • TAP III Beamforming System

    Publication Year: 1979, Page(s):6 - 13
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (563 KB)

    The Three Array Processor (TAP III) beamforming system incorporating both wideband time domain beamforming and narrowband frequency domain beamforming is described. The paper briefly develops the beamforming theory and shows how the Fast Fourier Transform (FFT) is applied to accomplish frequency domain beamforming. The use of a digital filtering and decimation technique to achieve very narrow freq... View full abstract»

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  • A Sonar Time Delay Using Charge-Coupled Devices (CCDs)

    Publication Year: 1979, Page(s):14 - 20
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (508 KB)

    The design of a time delay using a CCD as the linear delay element is described. The design objectives were a time delay of 160 ms for frequencies up to 14 kHz, and a dynamic range of 40 dB with a minimum signal to noise ratio of 12 dB. Three different commercial BBD and CCD parts were considered. Among problems addressed are the frequency response and some ways to compensate the severe high frequ... View full abstract»

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  • A Layer-Indexed Reflection Model for Multilayered Media

    Publication Year: 1979, Page(s):21 - 26
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (341 KB)

    Models for acoustic reflections from multilayered media, such as marine sediments or geological strata, are important for interpretive work on actual reflection data. We present here a new formulation for the ideal reflection process for multiple layers and unequal travel times. Our formulation uses a superior index notation, and gives a very tractable and compact model structure. We generalise th... View full abstract»

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  • A Wide Range Sonar System for Oceanic Investigations

    Publication Year: 1979, Page(s):27 - 32
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (587 KB)

    A modular, multi-channel sonar system capable of operation over the range from less than ten kilohertz to over one megahertz is described. The system features large dynamic range, low electronic noise level, variable output power to over one kilowatt and digital control of transmit and receive frequency. Capable of operation with a wide variety of transducers with only matching network changes, th... View full abstract»

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  • Undersea Acoustic Signal Coherence Fluctuations

    Publication Year: 1979, Page(s):33 - 39
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (523 KB)

    This paper describes the effects of source motion and multipath propagation in the ocean on the coherence of narrowband acoustic signals at widely spaced sonar receivers. The measure used to evaluate these effects is the magnitude-squared coherence (coherence). The discussion is based on both analytical developments and computer model studies. Definitions of coherence functions are presented. A ge... View full abstract»

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  • Directivity Index of Partially Random Sonobuoy Arrays

    Publication Year: 1979, Page(s):40 - 43
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (285 KB)

    The directivity index, DI, of partially random arrays is analyzed. A partially random array is an array in which the element positions are random variables subject to constraints that create some degree of either non-randomness or interdependence. The analysis is based on the definition of DI as the ratio in decibels of the power received by a single omnidirectional hydrophone of unity gain to the... View full abstract»

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  • Underwater Acoustic Instrumentation for Multi-Element Arrays

    Publication Year: 1979, Page(s):44 - 47
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (263 KB)

    Defence Research Establishment Atlantic (DREA) is engaged in a continuing program in underwater research in the oceans. As part of this program, a requirement exists to study the spatial coherence of sound fields. This paper discusses the design rationale and presents the typical specifications achieved with current DREA electronic data acquisition systems. These systems were developed and constru... View full abstract»

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  • Platform Location in Underwater Acoustics

    Publication Year: 1979, Page(s):48 - 53
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (366 KB)

    The paper analyses the problem of locating an undersea platform in time-space by passive acoustic techniques. The radiated signature of the platform is utilized to determine a collection of parameters,called a fix, from which the source/receiver geometry can be reconstructed. Two different configurations of important practical implication are considered. In one, a large array observes the spatial ... View full abstract»

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  • Suspended Kevlar Array Technology

    Publication Year: 1979, Page(s):54 - 58
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (484 KB)

    Considerable progress has been made with the evaluation, design, and utilization of Kevlar in ropes and cables since its initial introduction in the early 1970s. This paper briefly identifies this progress, but principally describes a significant example of the utility of the Kevlar technology in a joint United States/ New Zealand acoustic experiment conducted in the Fiji Basin. The Moored Acousti... View full abstract»

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  • Acoustic Measurement of Fish Schools Using Array Phase Information

    Publication Year: 1979, Page(s): 59
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (53 KB)

    The usefulness of side-looking sonar in fisheries assessment work can be greatly increased by employing array phase information to estimate the echo arrival direction. Vertical and horizontal coordinates (perpendicular to the beam direction) can be measured, permitting beam pattern corrections, tracking from ping to ping, and depth determination. Acoustic data have been gathered during cruises in ... View full abstract»

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  • Acoustic Techniques for Assessing the Density and Distribution of Suspended Particulate in the Marine Environment

    Publication Year: 1979, Page(s): 60
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (21 KB)

    Ecosystem studies often require measurement of particulate plumes generated by man-made changes in the natural environment. Deep ocean mining and coastal dredging are examples of these perturbations. The University of Washington Marine Acoustics Program has been studying the use of acoustic Techniques for detecting and quantifying plume density and distribution. Measurements have been made in mid-... View full abstract»

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  • The Application of Hydroacoustic Techniques to Determine the Spatial and Distribution and Abundance of Fishes in the Nearshore Area in the Vicinity of Thermal Generating Stations

    Publication Year: 1979, Page(s):61 - 63
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (234 KB)

    Hydroacoustic surveys of the nearshore population of fishes along the Southern California coastline have been conducted in the vicinity of thermal generating stations since 1976. A digital echo integration system was used in conjunction with Simrad EK 120 and Ross 105 kHz echo sounders. The nature of the hydroacoustic data made it far superior to net measurements of fish density because of the qua... View full abstract»

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  • A Versatile Sonar System for Fisheries Research and Management Applications

    Publication Year: 1979, Page(s):64 - 68
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (291 KB)

    An echo sounder has been developed with features ideally suited to the fisheries researcher and fisheries manager. Instruments commonly used for fisheries management and research are inaccurate, limited in dynamic range, unstable, and generally inflexible. An effort has been made to overcome these difficiencies with the echo sounder described in this paper. The echo sounder to be described has a t... View full abstract»

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  • Underwater Sound Signals Received on Geophones and Hydrophones off San Diego, California

    Publication Year: 1979, Page(s):69 - 74
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (426 KB)

    Low-frequency underwater sound signals from CW and explosive sources were received on both three-component geophones and hydrophones buried in the sediment offshore of Mission Beach, California, and recordings made. Analysis reveals that the N-S geophones provide a better S/N ratio for the shallow water (< 200 m) area west of the NOSC oceanographic tower, but that the hydrophones are better for... View full abstract»

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  • Limits on Signal Coherence in the Random Ocean Environment: An Overview

    Publication Year: 1979, Page(s):75 - 81
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (612 KB)

    There are many sources of acoustic signal fluctuations which set practical limits on coherent processing in space and time. In particular, the problem of acoustic fluctuations due to randomness in the ocean medium has received considerable recent attention. The purpose of this paper is to survey recent modeling approaches in this area, and also existing computer implementations of the models; it i... View full abstract»

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  • Wave Measurements Required for Acoustics

    Publication Year: 1979, Page(s): 82
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (25 KB)

    The analysis of the interaction of acoustic energy with the sea surface requires certain information about the sea surface. The purpose of this paper is to present to the measurement community the needs of the acoustics community. This paper addresses two areas of the problem: first, which characteristics of the sea surface significantly impact the scattering of acoustic energy; and second, how mi... View full abstract»

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  • An Oceanographic Model of Mesoscale Phenomena with Applications to Underwater Acoustics

    Publication Year: 1979, Page(s): 83
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (40 KB)

    First Page of the Article
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  • Acoustic Propagation in Surface Duets Using the Radiation Transport Equation

    Publication Year: 1979, Page(s):84 - 91
    Cited by:  Papers (1)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (631 KB)

    A new theoretical approach to modeling underwater acoustic propagation is described. Based on the radiation transport equation, this technique easily allows incorporation of scattering by rough surfaces and internal waves. It has been applied to the problem of surface duct propagation with special emphasis on modeling the scattering out of the duct by rough surfaces and random fluctuations resulti... View full abstract»

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  • A Unified Method of Broadband Acoustic Characterization for Fish Schools, Channels, and Range-Extended Targets

    Publication Year: 1979, Page(s):92 - 99
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (591 KB)

    Fish schools and long-range propagation channels can be described by a scattering function, i.e., by the expected distribution of Doppler shifts and delays that are introduced by a collection of moving point scatterers. Acoustic inhomogeneities such as man-made objects and minerals on or below the ocean floor can be characterized by the frequency dependence of sound absorption and reflectivity, an... View full abstract»

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  • The Measurements of Relative Q of Ocean Sub-Bottom by Digital Signal Processing Techniques

    Publication Year: 1979, Page(s):100 - 103
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (259 KB)

    Using a Fast Fourier transform algorithms, the remotely obtained digitized real time acoustic data of the subbottom is converted into a frequency domain representation for both the input and the reflected pulses. Since the digitized time series resembles damped harmonic oscillators, the frequency domain representation of the pulses - input and reflected - is used in the measurement of Q. This meas... View full abstract»

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  • CCD/SAW Sonar Beamforming

    Publication Year: 1979, Page(s):104 - 108
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (313 KB)

    Charge-coupled devices (CCD's) have been used to scan convert sonar data rates to speeds where surface acoustic wave (SAW) technology is applicable. A discrete Fourier transform has been implemented with SAW's using the Chirp-Z Transform (CZT) algorithm. Beamforming techniques to focus in the nearfield for high resolution arrays are shown. The beam output rate is inversely proportional to the samp... View full abstract»

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  • Coherent Detection of Signals with Time-Varying Parameters Using Multiple Observations

    Publication Year: 1979, Page(s):109 - 111
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (219 KB)

    This paper investigates the multiple observation detection statistic computed as the average of a non-overlapping time-sequence of magnitude-squared coherence (MSC) statistics, denoted AMSC. The multiple observation statistic provides a means to counteract the decrease in MSC detection performance caused by variation of the unknown signal parameters. This variation may be attributed to boundary ch... View full abstract»

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