Modal analysis of broadband acoustic receptions at 3515-km range in the North Pacific using short-time Fourier techniques

Wage, Kathleen E.; Baggeroer, Arthur B.; Preisig, James C.

doi:10.1121/1.1530615

Cited by 47 publications

(48 citation statements)

References 32 publications

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“…Second, for both regimes it has been shown that the edges of the shadow zones of the wavefront are significantly extended in depth, and in time [19,20][26]This extension of the shadow zone shows that the effect of scattering in long range low frequency ocean acoustic propagation is to introduce a significant bias into the wavefront intensity pattern; that is to say, the acoustic fluctuations cannot be considered a zero mean effect superimposed upon an otherwise deterministic wavefront pattern. Finally, in spite of the large fluctuations in the wavefront finale the time stability of the phase is surprisingly large and close to that of the wavefront region [22,79,30]. Observed coherence times are between 5 and 15 minutes.…”

Section: Discussionmentioning

confidence: 83%

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Xu¹

2007

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This thesis covers a comprehensive analysis of long-range, deep-ocean, low-frequency, sound propagation experimental results obtained from the North Pacific Ocean. The statistics of acoustic fields after propagation through internal-wave-induced sound-speed fluctuations are explored experimentally and theoretically.The thesis starts with the investigation of the North Pacific Acoustic Laboratory 98-99 data by exploring the space-time scales of ocean sound speed variability and the contributions from different frequency bands. The validity of the Garret & Munk internal-wave model is checked in the upper ocean of the eastern North Pacific. All these results impose hard bounds on the strength and characteristic scales of sound speed fluctuations one might expect in this region of the North Pacific for both internal-wave band fluctuations and mesoscale band fluctuations.The thesis then presents a detailed analysis of the low frequency, broadband sound arrivals obtained in the North Pacific Ocean. The observed acoustic variability is compared with acoustic predictions based on the weak fluctuation theory of Rytov, and direct parabolic equation Monte Carlo simulations. The comparisons show that a resonance condition exists between the local acoustic ray and the internal wave field such that only the internal-waves whose crests are parallel to the local ray path will contribute to acoustic scattering: This effect leads to an important filtering of the acoustic spectra relative to the internal-wave spectra. We believe that this is the first observational evidence for the acoustic ray and internal wave resonance.Finally, the thesis examined the evolution with distance, of the acoustic arrival pattern of the off-axis sound source transmissions in the Long-range Ocean Acoustic Propagation EXperiment. The observations of mean intensity time-fronts are compared to the deterministic ray, parabolic equation (with/without internal waves) and (one-way coupled) normal mode calculations. It is found the diffraction effect is dominant in the shorter-range transmission. In the longer range, the (internal wave) scattering effect smears the energy in both the spatial and temporal scales and thus has a dominant role in the finale region.

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Section: Discussionmentioning

confidence: 83%

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Xu¹

2007

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“…The mth row of the beampattern matrix corresponds to the projection of the modes into the estimate for mode m. The PI filter is constrained pass the desired mode with unity gain and place nulls at the location of other modes included in the pseudo-inverse. It does not constrain the output at modes not included in the pseudo-inverse [9]. The beampattern in Figure 1(b) is for a 20-mode processor, thus the beampattern shows a diagonal structure up to mode 20.…”

Section: W'mentioning

confidence: 97%

“…See the papers by Wage et til. for more information about mode filtering methods [9,10]. Figure 2 shows an example of the received signals at the VLA from each of the two sources and the corresponding estimated time series for modes 1, 5, and 10.…”

Section: W'mentioning

confidence: 99%

Design of Robust Adaptive Array Processors for Non-Stationary Ocean Environments

Wage¹

2009

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Office of Naval Research 100 Alabama St., SW Suite4R15 Atlanta, GA 30303-3104 SPONSOR/MONITOR'S ACRONYM(S) ONR SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for Public Release; Distribution is Unlimited SUPPLEMENTARY NOTES ABSTRACTThe overall goal of this project is to design adaptive array processing algorithms that have good transient performance, are robust to mismatch, work with low sample support, and incorporate waveguide physics in a meaningful and robust way. To develop improved array processing algorithms for non-stationary environments, this project is investigating adaptive beamforming algorithms that can operate on a single-snapshot or a very limited number of snapshots. Spectral estimation methods, such as the multitaper spectral estimator developed by Thomson [Proc. IEEE, 1982] require only a single snapshot to produce an estimate. This project explores how to adapt the multitaper approach to the spatial spectral estimation problem. SUBJECT TERMSSignal processing, Adaptive array processing, underwater acoustic propagation LONG-TERM GOALSThe overall goal of this project is to design adaptive array processing algorithms that have good transient performance, are robust to mismatch, work with low sample support, and incorporate waveguide physics in a meaningful and robust way.

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“…The problems in undersized sparse vertical arrays were investigated in [8]. The comparison of different approaches to mode coefficients estimation was conducted in [5], [11], and [12]. In accordance with referenced sources, pseudoinverse transformation (PI) is a very reasonable method for mode coefficient estimation when the signal-to-noise ratio (SNR) is much larger than one.…”

Section: Investigation Of Mode Filtering As a Preprocessing Methods Fomentioning

confidence: 99%

“…Inverse matrixes are frequency dependent and in a broadband case must be applied for each frequency in the signal spectrum. This broadband approach was considered in many papers for a number of different applications: [6], [8], [25], [9], [11], [12]. In these works, the mode coefficients are expected to be constant during the interval of Fourier transformation.…”

Section: The Basics Of Acoustic Field Normal-mode Decomposition Amentioning

confidence: 99%

Investigation of Mode Filtering as a Preprocessing Method for Shallow-Water Acoustic Communications

Morozov

Preisig

Papp

2010

IEEE J. Oceanic Eng.

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Abstract-Acoustical array data from the 2006 Shallow Water Experiment (SW06) was analyzed to show the feasibility of broadband mode decomposition as a preprocessing method to reduce the effective channel delay spread and concentrate received signal energy in a small number of independent channels. The data were collected by a vertical array, which spans the water column from 12-m depth to the bottom in shallow water 80 m in depth. Binary -sequence data were used to phase-shift-keyed (PSK) modulate signals with different carrier frequencies. No error correction coding was used. The received signals were processed by a system that does not use training or pilot signals. Signals received both during periods of ordinary internal wave activity and during a period with unusually strong internal wave solitons were processed and analyzed. Different broadband mode-filtering methods were analyzed and tested. Broadband mode filtering decomposed the received signal into a number of independent signals with a reduced delay spread. The analysis of signals from the output of mode filters shows that even a simple demodulator can achieve a low bit error rate (BER) at a distance 19.2 km.Index Terms-Signal processing, underwater acoustic arrays, underwater acoustic communications.

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Modal analysis of broadband acoustic receptions at 3515-km range in the North Pacific using short-time Fourier techniques

Cited by 47 publications

References 32 publications

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Design of Robust Adaptive Array Processors for Non-Stationary Ocean Environments

Investigation of Mode Filtering as a Preprocessing Method for Shallow-Water Acoustic Communications

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