Interference of wide-band sound in shallow water

Weston, D. E.; Stevens, Karen

doi:10.1016/0022-460x(72)90205-2

Cited by 32 publications

(13 citation statements)

References 8 publications

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“…7,23 The relationship between the first term and the third term shows that increasing the channel depth also increases the focal range, which was observed as a mirage effect in matched-field processing 22 and a shift of interference patterns caused by tidal variations. 26 This expression also explains the internal-waveinduced focal shift observed in the simulation results. The internal-wave displacement changes the thermocline depth.…”

Section: ͑11͒mentioning

confidence: 58%

Robust time reversal focusing in the ocean

Kim

Kuperman

Hodgkiss

et al. 2003

The Journal of the Acoustical Society of America

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Recent time-reversal experiments with high-frequency transmissions (3.5 kHz) show that stable focusing is severely limited by the time-dependent ocean environments. The vertical focal structure displays dynamic variations associated with focal splitting and remerging resulting in large changes in focal intensity. Numerical simulations verify that the intensity variation is linked to the focal shift induced by phase changes in acoustic waves resulting from sound speed fluctuations due to internal waves. A relationship between focal range shift, frequency shift, or channel depth changes is illustrated using waveguide-invariant theory. Based on the analysis of experimental data and numerical simulations, methods for robust time-reversal focusing are developed to extend the period of stable focusing.

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Section: ͑11͒mentioning

confidence: 58%

Robust time reversal focusing in the ocean

Kim

Kuperman

Hodgkiss

et al. 2003

The Journal of the Acoustical Society of America

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“…Hanna and Rost (1981) noted the lack of deep nulls in transmission loss derived from shot experiments, and the resemblance between a frequency average and a range average (although not quite the same type as advocated here). Also the underlying relationship between range and frequency shifts in interference patterns has been explored theoretically and experimentally by Weston and Rowlands (1979) and Weston and Stevens (1972).…”

Section: Introductionmentioning

confidence: 98%

A simple relationship between frequency and range averages for broadband sonar

Harrison¹,

Harrison²

1995

The Journal of the Acoustical Society of America

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All sonars have a bandwidth, and often the assumption of single frequency propagation will mislead the sonar designer. It is shown here theoretically, and by demonstration using SAFARI, that a frequency average can often be approximated closely by a variable width running range average in which the width or window size is proportional to range. In fact if the bandwidth is expressed as a fraction a of the center frequency one should use a range averaging width of a times the range. The limitations of such a scheme are also addressed.

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“…Multipath interference is the result of time delays between arrivals causing constructive and destructive interference at different frequencies (Harrison, 2011). It has been the subject of much study because the pattern often has low sensitivity to waveguide parameters (Weston and Stevens, 1972). The technique presented in this chapter bypasses the interference pattern and directly measures the time delays between arrivals by cross correlating beams steered at multipath arrivals.…”

Section: Chapter 6 Volumetric Array Processingmentioning

confidence: 99%

“…The novel contributions of this study are centered on methodology and signal processing. Until fairly recently estimating the range of a target using its received multipath (often referred to as "multipath ranging"), focused on the interference pattern created by the multipath arrivals (Weston and Stevens, 1972). This made sense because the broadband noise of a boat can be approximated as a random process, but between multipath arrivals there is coherence, or predictability.…”

Section: Introductionmentioning

confidence: 99%

Advances in Aquatic Target Localization with Passive Sonar

Gebbie¹

2000

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New underwater passive sonar techniques are developed for enhancing target localization capabilities in shallow ocean environments. The ocean surface and the seabed act as acoustic mirrors that reflect sound created by boats or subsurface vehicles, which gives rise to echoes that can be heard by hydrophone receivers (underwater microphones). The goal of this work is to leverage this "multipath" phenomenon in new ways to determine the origin of the sound, and thus the location of the target. However, this is difficult for propeller driven vehicles because the noise they produce is both random and continuous in time, which complicates its measurement and analysis. Further, autonomous underwater vehicles (AUVs) pose additional challenges because very little is known about the sound they generate, and its similarity to that of boats. Existing methods for localizing propeller noise using multiple hy- iii

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Interference of wide-band sound in shallow water

Cited by 32 publications

References 8 publications

Robust time reversal focusing in the ocean

Robust time reversal focusing in the ocean

A simple relationship between frequency and range averages for broadband sonar

Advances in Aquatic Target Localization with Passive Sonar

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