Inversion for geometric and geoacoustic parameters in shallow water: Experimental results

Gingras, D.F.; Gerstoft, Peter

doi:10.1121/1.412442

Cited by 112 publications

(65 citation statements)

References 15 publications

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“…The SCARAB'97 experiment was conducted in June, so the measured sound speed profiles were downward refracting. The bottom properties in the Capraia basin have been the subject of considerable study [4,5]; here we adopt a fast upwardly refracting bottom used by Jensen to adequately characterize the transmission loss [6]. The sound speed profile in the water column and into the bottom is illustrated in Fig.…”

Section: Resultsmentioning

confidence: 99%

Bottom reverberation in shallow water: Coherent properties as a function of bandwidth, waveguide characteristics, and scatterer distributions

LePage

1999

The Journal of the Acoustical Society of America

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Shallow water presents a difficult, reverberation-limited environment for active SONAR operations. It is important to understand the predictable structure of shallow-water reverberation in order to aid the design of processors and detectors which work properly in these environments. In this paper, the temporal characteristics of monostatic reverberation are predicted as a function of source bandwidth, source–receiver depth, and the propagation characteristics of range-independent shallow water. Results show that at early time, reverberation can be highly coherent across a vertical line array, violating the homogeneous noise assumption, while at late time the reverberation becomes increasingly uncorrelated. This is shown to be due to the insonification of independent bottom patches at late time. It is also shown that this decorrelation of the reverberation is dependent both on the propagation characteristics of the particular shallow-water environment, the correlation length scale of the scatterers, and the bandwidth of the source, with high-bandwidth sources causing decorrelated reverberation sooner than low-bandwidth sources. The results also show that there are several identifying characteristics in reverberation time series which may be useful for identifying the types of scatterers which cause reverberation during particular experiments.

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Section: Resultsmentioning

confidence: 99%

Bottom reverberation in shallow water: Coherent properties as a function of bandwidth, waveguide characteristics, and scatterer distributions

LePage

1999

The Journal of the Acoustical Society of America

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“…The approach proposed in this study is also evaluated using vertical array data collected during the October 1993 Mediterranean Sea Trials [21,22] spacing. The source signal was pseudo-random noise in a 20 Hz band around 170 Hz, whose −3 dB bandwidth was approximately 12 Hz, and the sampling frequency was 1 kHz.…”

Section: Experiments Descriptionmentioning

confidence: 99%

Matched-field localization using a virtual time-reversal processing method in shallow water

Zhang

Yang

2011

Chin. Sci. Bull.

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Time-reversal processing (TRP) is an implementation of matched-field processing (MFP) where the ocean itself is used to construct the replica field. This paper introduces virtual time-reversal processing (VTRP) that is implemented electronically at a receiver array and simulates the kind of processing that would be done by an actual TRP during the reciprocal propagation stage. MFP is a forward propagation process, while VTRP is a back-propagation process, which exploits the properties of reciprocity and superposition and is realized by weighting the replica surface with the complex conjugate of the data received on the corresponding element, followed by summation of the processed received data. The number of parabolic equation computational grids of VTRP is much smaller than that of MFP in a range-dependent waveguide. As a result, the localization surface of VTRP can be formed faster than its MFP counterpart in a range-dependent waveguide. The performance of VTRP for source localization is validated through numerical simulations and data from the Mediterranean Sea. Time-reversal processing (TRP) [1][2][3][4][5][6][7] is a process of retransmitting a received signal in a time-reversed fashion by a source-receiver array. In the frequency domain, time reversal is equivalent to phase conjugation. When TRP is applied to source localization, known as virtual time-reversal processing (VTRP), it is unnecessary to send a signal back and forth between the source and receiver. Instead, assuming that the acoustic channel is sufficiently stable in time, the retransmission of the temporal dispersed signals in a time reversed fashion will be done by a computer. A passive array is used in VTRP instead of a source-receiver array.When TRP is applied to source localization, there is one drawback to this back-propagation approach. Because of sound attenuation, the acoustic intensity close to the "source-receiver" array is much stronger than the focusing peak at the real source location. This means that the focusing peak is only a local maximum around the real source *Corresponding author (email: walternwpu@gmail.com) location rather than a global one. To suppress the stronger peaks close to the passive array and make the focusing peak the global maximum, an appropriate normalization factor should be introduced to the back-propagation field. Therefore, the localization surface formed by VTRP contains the focusing peak, which provides the greatest likelihood of the source location.Matched-field processing (MFP) and VTRP are conceptually similar, but differ in their physical meaning and physical implementation. MFP [8-13] is a forward propagation process that consists of systematically placing a test point source at each point of a search grid, computing the replica vectors on the array and then correlating these replicas with the data from the real source. A search is performed in a region of possible target positions. VTRP is a back-propagation process which exploits the properties of medium reciprocity and superposition. VTRP ca...

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“…Consider a vertical array of 24 hydrophones place every 4 meters in depth from 18.7 to 110.7 m. The water depth is 127 m. The other environmental parameters are the same as in ref. [41]. The sea environment is isotropic, i.e.…”

Section: Generalized Spatial Filtermentioning

confidence: 99%

Optimal design and verification of temporal and spatial filters using second-order cone programming approach

Yan

2006

SCI CHINA SER F

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Temporal filters and spatial filters are widely used in many areas of signal processing. A number of optimal design criteria to these problems are available in the literature. Various computational techniques are also presented to optimize these criteria chosen. There are many drawbacks in these methods. In this paper, we introduce a unified framework for optimal design of temporal and spatial filters. Most of the optimal design problems of FIR filters and beamformers are included in the framework. It is shown that all the design problems can be reformulated as convex optimization form as the second-order cone programming (SOCP) and solved efficiently via the well-established interior point methods. The main advantage of our SOCP approach as compared with earlier approaches is that it can include most of the existing methods as its special cases, which leads to more flexible designs. Furthermore, the SOCP approach can optimize multiple required performance measures, which is the drawback of earlier approaches. The SOCP approach is also developed to optimally design temporal and spatial two-dimensional filter and spatial matrix filter. Numerical results demonstrate the effectiveness of the proposed approach.

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Inversion for geometric and geoacoustic parameters in shallow water: Experimental results

Cited by 112 publications

References 15 publications

Bottom reverberation in shallow water: Coherent properties as a function of bandwidth, waveguide characteristics, and scatterer distributions

Bottom reverberation in shallow water: Coherent properties as a function of bandwidth, waveguide characteristics, and scatterer distributions

Matched-field localization using a virtual time-reversal processing method in shallow water

Optimal design and verification of temporal and spatial filters using second-order cone programming approach

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