Features of the Heard Island signals received at Ascension

Georges, T. M.; Boden, Linda; Palmer, David R.

doi:10.1121/1.410116

Cited by 7 publications

(4 citation statements)

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“…Georges et al ͑1994͒ measured the phase rate on a propagation path from Heard Island to Ascension Island. 11 At a frequency of 57 Hz and source-receiver range of 9100 km, they found / f to lie between 2.3ϫ 10 −6 and 7.0ϫ 10 −6 . Birdsall et al ͑1994͒ measured the phase rate of the same signal from Heard Island to Kiritimati ͑Christmas͒ Island 12 and found / f to not exceed 35ϫ 10 −6 at a range of 5510 km.…”

Section: A Experimental Resultsmentioning

confidence: 97%

“…Most of the experimental measurements in deep water use a narrow band signal. [4][5][6][7][8][9][10][11][12][13] Note that a true continuous wave ͑cw͒ signal has a constant phase in the base band. In a time-varying medium, the phase of the cw signal ͑for a single path arrival͒ in the base band changes with time, causing an increase in the signal bandwidth ͑Doppler spread͒.…”

Section: Review Of Temporal Coherence In Deep Watermentioning

confidence: 99%

“…Fitzgerald et al 10 focused on 10 Hz signal propagation in the Hatteras Abyssal Plain in 1976. Georges et al 11 and Birdsall et al 12 investigated 57 Hz signal propagation to thousands of kilometers from the Heart Island in 1994. Parvulescu 13 reported his earlier work on matched-signal processing in 1995.…”

Section: Introductionmentioning

confidence: 99%

“…11. ͑Color online͒ Comparison of the modeled coherence time 0.8 ͑denoted by ϩ͒ with the ADVENT99 data as displayed inFig.…”

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confidence: 99%

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Temporal coherence of sound transmissions in deep water revisited

Yang

2008

The Journal of the Acoustical Society of America

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This paper examines the signal coherence loss due to internal waves in deep water in terms of the signal coherence time and compare to data reported in the literature over the past 35 years. The coherence time of the early raylike arrivals was previously modeled by Munk and Zachariasen ["Sound propagation through a fluctuating stratified ocean: Theory and observation," J. Acoust. Soc. Am. 59, 818-838 (1976)] using the supereikonal approximation and by Dashen et al. ["Path-integral treatment of acoustic mutual coherence functions for arrays in a sound channel," J. Acoust. Soc. Am. 77, 1716-1722 (1985)] using the path integral approach; a -1 [corrected] power frequency dependence and a -1/2 [corrected] power range dependence were predicted. Recent data in shallow water in downward refractive environments with internal waves suggested that the signal coherence time of the mode arrivals follows a -3/2 power frequency dependence and a -1/2 power range dependence. Since the temporal coherence of the acoustic signal is related to the temporal coherence of the internal waves, based on the observation that the (linear) internal waves in deep and shallow waters have a similar frequency spectrum, it is argued that the modelike arrivals in deep water should exhibit a similar frequency dependence in deep and shallow waters. This argument is supported by a brute-force application of the path integral to mode arrivals based on the WKB relation between the ray and mode. It is found that the data are consistent with the -3/2 power frequency dependence but more data are needed to further test the hypothesis.

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Section: A Experimental Resultsmentioning

confidence: 97%