High-frequency acoustic echoes received from simple geometric shapes with possible applications to target recognition

Dunsiger, A.D.

doi:10.1016/s0022-460x(70)80022-0

Cited by 8 publications

(3 citation statements)

References 14 publications

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“…Consider a shock wave (impulse) impinging on a sphere of radius a. To a first approximation, using the image-pulse theory developed by Freedman [7][8][9][10], the first two artefacts of the backscattered impulse response will consist of two impulses of opposing sign separated by a time duration 2a/c. If the magnitude of these two impulses is approximately equal then the backscattered frequency response will approximate to…”

Section: Fig 2 First Two Impulses Of Backscattered Signalmentioning

confidence: 99%

Calibration of broadband sonar systems using multiple standard targets

Atkins

Francis

Foote

2008

The Journal of the Acoustical Society of America

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A seven-octave active sonar system spanning the nominal frequency range 25-3200 kHz was deployed in Norwegian waters for the purpose of measuring the acoustic scattering characteristics of a range of marine organisms. This system transmitted linear frequency-modulated (LFM) signals in order to achieve good range resolution and to obtain spectral information on resolved targets. Total system performance was variously measured in situ and ex situ, depending on the particular octave band, using standard-target spheres. This enabled the frequency response of the entire system to be determined and the sidelobe level of the matched-filter receiver to be reduced. The effects of the deep nulls encountered in the backscattered spectrum of target spheres were partially reduced by using a string of up to six spheres of different sizes and material properties. Typical results will be presented showing that such calibration procedures are sensitive to the relative alignment of the sonar-target and to sound-speed profile changes over the length of the string.

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Section: Fig 2 First Two Impulses Of Backscattered Signalmentioning

confidence: 99%

Calibration of broadband sonar systems using multiple standard targets

Atkins

Francis

Foote

2008

The Journal of the Acoustical Society of America

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“…For a cylindrical body, the factor 1/2 is not present in either Eq (27) or Eq (29), but for spherical bodies, it is. The pole position, for given values of n and /, is labeled in the diagram by ni + 1/2 in the spherical case, and by «/ in the cylindrical case.…”

Section: Re (Inmentioning

confidence: 99%

“…This information, which includes the phase/group velocities of the surface waves and the aspect ratio of the spheroidal shell, is to be added to the large number of features [27,126] that can be extracted from sonar echoes [40,41]. We are not aware of any work on viscoelastically coated spheroidal shells.…”

Section: Effects Of Arbitrary Incidences On a Spheroidal Shellmentioning

confidence: 99%

Acoustic Resonance Scattering by Submerged Elastic Shells

Gaunaurd

Werby²

1990

Applied Mechanics Reviews

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We review a number of instances in which classical acoustic wave scattering from submerged elastic shells can be analyzed in the resonance region of their spectra. We recently reviewed (Refs 42,43,12) the cases dealing with acoustic resonance scattering from solid elastic bodies, or with elastic resonance scattering from fluid or solid inclusions in elastic media. It only remains for us to address the works dealing with submerged shells, which we analyze here. We study scattering by bare or viscoelastically coated spherical and cylindrical shells in water, by means of (exact) normal-mode solutions, and by spheroidal shells by numerical approaches, particularly via the T-matrix method. We consider the shell responses mostly in unbounded media and when the interrogating waves are plane and c.w., although some recent findings valid for pulsed incidences and in the vicinity of environmental boundaries are also included. We use the methodology of the resonance scattering theory (RST) as much as possible, emphasizing its post-1981 results. High-frequency findings, obtained by asymptotic methods, are extrapolated to lower frequencies, to confirm RST predictions for the intermediate spectral regions in which the most important structural resonances are known to reside. A large number of bibliographical entries are collected and discussed in connection with our approach.Downloaded From: http://appliedmechanicsreviews.asmedigitalcollection.asme.org/ on 05/24/2015 Terms of Use: http://asme.org/terms Gaunaurd and Werby: Acoustic resonance scattering

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Flaw characterization based on diffraction of ultrasonic waves

Lam

Tsang

1985

Ultrasonics

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High-frequency acoustic echoes received from simple geometric shapes with possible applications to target recognition

Cited by 8 publications

References 14 publications

Calibration of broadband sonar systems using multiple standard targets

Calibration of broadband sonar systems using multiple standard targets

Acoustic Resonance Scattering by Submerged Elastic Shells

Flaw characterization based on diffraction of ultrasonic waves

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