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Full-Text Articles in Engineering
Head-Wave Correlations In Layered Seabed: Theory And Modeling, Jie Li, Martin Siderius, Peter Gerstoft, Jun Fan, Lanfranco Muzi
Head-Wave Correlations In Layered Seabed: Theory And Modeling, Jie Li, Martin Siderius, Peter Gerstoft, Jun Fan, Lanfranco Muzi
Electrical and Computer Engineering Faculty Publications and Presentations
This paper derives travel times and arrival angles of head-wave correlations from ocean ambient noise in shallow water over a layered seabed. The upcoming and surface reflected head-wave noise signal received at two receivers from the same interface are correlated, and their travel time differences give the travel times of the head-wave correlations. The arrival angle of head-wave correlations from an interface depends on sound speeds in the layers above and just below. The predictions of head-wave correlations from a seabed with two layers and the corresponding inversion results are verified with simulations.
Inversion Of Head Waves In Ocean Acoustic Ambient Noise, Jie Li, Peter Gerstoft, Martin Siderius, Jun Fan
Inversion Of Head Waves In Ocean Acoustic Ambient Noise, Jie Li, Peter Gerstoft, Martin Siderius, Jun Fan
Electrical and Computer Engineering Faculty Publications and Presentations
The virtual head wave is produced through cross-correlation processing of signals containing the real, acoustic head wave. The virtual head wave has the same phase speed as the head wave, but the travel time is offset, thus the term virtual. The virtual head wave, like the real head wave, propagates in a direction corresponding to the seabed critical angle. The virtual head wave travel time varies with array depth and water column depth. However, in a refracting environment, the travel time is also dependent on the depth-dependent sound speed profile. Previously, the virtual head wave was shown as observable from …
Environmental Information Content Of Ocean Ambient Noise, Martin Siderius, John Thomas Gebbie
Environmental Information Content Of Ocean Ambient Noise, Martin Siderius, John Thomas Gebbie
Electrical and Computer Engineering Faculty Publications and Presentations
In recent years, methods have been developed to estimate a variety of environmental parameters based on measurements of the ocean ambient noise. For example, noise has been used to estimate water depth using the passive fathometer technique and bottom loss estimated and used to invert for seabed parameters. There is also information in the noise about the water column sound speed, volume attenuation, and the sea-state. The Fisher information can be used to quantify the basic information available in the noise measurements and its inverse, the Cramér–Rao lower bound (CRLB), provides the lower limit on the variance of an unbiased …
Frequency Based Noise Coherence-Function Extension And Application To Passive Bottom-Loss Estimation, Lanfranco Muzi, Martin Siderius, Peter L. Nielsen
Frequency Based Noise Coherence-Function Extension And Application To Passive Bottom-Loss Estimation, Lanfranco Muzi, Martin Siderius, Peter L. Nielsen
Electrical and Computer Engineering Faculty Publications and Presentations
Accurate modeling of acoustic propagation in the ocean waveguide is important to SONAR-performance prediction. Particularly in shallow waters, a crucial contribution to the total transmission loss is the bottom refection loss, which can be estimated passively by beamforming the natural surface-noise acoustic field recorded by a vertical line array of hydrophones. However, the performance in this task of arrays below 2 m of length is problematic for frequencies below 10 kHz" role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px 2px 0px …
Exploitation Of Frequency Information In Continuous Active Sonar, Lisa Zurk, Daniel Rouseff, Scott Schecklman
Exploitation Of Frequency Information In Continuous Active Sonar, Lisa Zurk, Daniel Rouseff, Scott Schecklman
Electrical and Computer Engineering Faculty Publications and Presentations
In pulsed active sonar, short duration coded waveforms insonify the area of interest. The low duty cycle limits detection opportunities and decreases average energy. A recent concept is continuous active sonar (CAS), which has continuous source transmission over a broad frequency band. The low duty cycle limits detection opportunities and decreases average energy. A recent concept is continuous active sonar (CAS), which has continuous source transmission over a broad frequency band. Previous work by the authors has investigated the utility of extracting the propagation-induced frequency structure in pulsed sonar. The broadband, continuous CAS waveforms particularly lend themselves to this approach. …
Head Wave Correlations In Ambient Noise, John Thomas Gebbie, Martin Siderius
Head Wave Correlations In Ambient Noise, John Thomas Gebbie, Martin Siderius
Electrical and Computer Engineering Faculty Publications and Presentations
Ambient ocean noise is processed with a vertical line array to reveal coherent time-separated arrivals suggesting the presence of head wave multipath propagation. Head waves, which are critically propagating water waves created by seabed waves traveling parallel to the water-sediment interface, can propagate faster than water-only waves. Such eigenrays are much weaker than water-only eigenrays, and are often completely overshadowed by them. Surface-generated noise is different whereby it amplifies the coherence between head waves and critically propagating water-only waves, which is measured by cross-correlating critically steered beams. This phenomenon is demonstrated both experimentally and with a full wave simulation.
Coherence Extrapolation For Underwater Ambient Noise, Jorge Quijano, Stan E. Dosso, Martin Siderius, Lanfranco Muzi
Coherence Extrapolation For Underwater Ambient Noise, Jorge Quijano, Stan E. Dosso, Martin Siderius, Lanfranco Muzi
Electrical and Computer Engineering Faculty Publications and Presentations
This paper considers extrapolation of the vertical coherence of surface-generated oceanic ambient noise to simulate measurements made on a longer sensor array. The extrapolation method consists of projecting the noise coherence measured with a limited aperture array into the domain spanned by prolate spheroidal wave functions, which are an orthogonal basis defined by array parameters and the noise frequency. Using simulated data corresponding to selected multi-layered seabeds as ground truth, the performance of the extrapolation method is explored. Application of the technique is also demonstrated on experimental data.
Localization Of A Noisy Broadband Surface Target Using Time Differences Of Multipath Arrivals, John Gebbie, Martin Siderius, Reid Mccargar, John S. Allen Iii, Grant Pusey
Localization Of A Noisy Broadband Surface Target Using Time Differences Of Multipath Arrivals, John Gebbie, Martin Siderius, Reid Mccargar, John S. Allen Iii, Grant Pusey
Electrical and Computer Engineering Faculty Publications and Presentations
Previous studies [Tiemann et al., J. Acoust. Soc. Am. 120, 2355–2365 (2006)] have reported the localization of marine mammals in 3-D from their clicks using multipath arrivals. Bathymetric variations were advantageously used to predict multipath arrival times with a raytracer. These arrivals are directly discernible from the time series for impulsive sources, such as whale clicks, but extension of the method to continuous broadband sources presents additional complications. By pulse compressing noise emitted from a small boat using two hydrophones,the hyperbolic direct-arrival ambiguity can be refined in both range and bearing. Acoustic-derived results are validated with target GPS measurements.
Synthetic Array Processing Of Ocean Ambient Noise For Higher Resolution Seabed Bottom Loss Estimation, Martin Siderius, Lanfranco Muzi, Chris H. Harrison, Peter L. Nielsen
Synthetic Array Processing Of Ocean Ambient Noise For Higher Resolution Seabed Bottom Loss Estimation, Martin Siderius, Lanfranco Muzi, Chris H. Harrison, Peter L. Nielsen
Electrical and Computer Engineering Faculty Publications and Presentations
Predicting transmission loss in the ocean often strongly depends on the bottom loss. Bottom loss can be estimated using ocean noise and vertical array beam-forming [Harrison and Simons, J. Acoust. Soc. Am. 112, 1377–1389 (2002)]. With finite length arrays, the bottom loss estimate using this method can be smoothed due to beam widths. This paper describes how the noise coherence function can be synthetically expanded, which is similar to extending the length of an array. A full wave ocean noise model is used to demonstrate, in simulation, how this leads to improvements in the resolution of bottom loss estimates.
Trans-Dimensional Geoacoustic Inversion Of Wind-Driven Ambient Noise, Jorge E. Quijano, Stan E. Dosso, Jan Dettmer, Lisa M. Zurk, Martin Siderius
Trans-Dimensional Geoacoustic Inversion Of Wind-Driven Ambient Noise, Jorge E. Quijano, Stan E. Dosso, Jan Dettmer, Lisa M. Zurk, Martin Siderius
Electrical and Computer Engineering Faculty Publications and Presentations
This letter applies trans-dimensional Bayesian geoacoustic inversion to quantify the uncertainty due to model selection when inverting bottom-loss data derived from wind-driven ambient-noise measurements. A partition model is used to represent the seabed, in which the number of layers, their thicknesses, and acoustic parameters are unknowns to be determined from the data. Exploration of the parameter space is implemented using the Metropolis–Hastings algorithm with parallel tempering, whereas jumps between parameterizations are controlled by a reversible-jump Markov chain Monte Carlo algorithm. Sediment uncertainty profiles from inversion of simulated and experimental data are presented.
Using Practical Supergain For Passive Imaging With Noise, Martin Siderius
Using Practical Supergain For Passive Imaging With Noise, Martin Siderius
Electrical and Computer Engineering Faculty Publications and Presentations
Recent work has shown that endfire beamforming of ocean noise can be used to produce images of the seabed layering [Siderius et al., J. Acoust. Soc. Am. 120, 1315–1323 (2006)]. This initial noise imaging technique used conventional beamforming and was later extended to adaptive beamforming that is theoretically optimal. However, there can be problems with adaptive methods, which include extreme sensitivity to random errors, the required averaging time, and computational complexity. Here, the concept of supergain is used to show that delay and sum beamforming can produce nearly the same results as the optimal adaptive methods without the drawbacks.
Striation-Based Beamforming For Estimating The Waveguide Invariant With Passive Sonar, Lisa M. Zurk, Daniel Rouseff
Striation-Based Beamforming For Estimating The Waveguide Invariant With Passive Sonar, Lisa M. Zurk, Daniel Rouseff
Electrical and Computer Engineering Faculty Publications and Presentations
The waveguide invariant summarizes the pattern of constructive and destructive interference between acoustic modes propagating in the ocean waveguide. For many sonar signal-processing schemes, it is essential to know the correct numerical value for the waveguide invariant. While conventional beamforming can estimate the ratio between the waveguide invariant and the range to the source, it cannot unambiguously separate the two terms. In the present work, striationbased beamforming is developed. It is shown that the striation-based beamformer can be used to produce an estimate for the waveguide invariant that is independent of the range. Simulation results are presented.
Extraction Of Small Boat Harmonic Signatures From Passive Sonar, George Lloyd Ogden, Lisa M. Zurk, M. E. Jones, M. E. Peterson
Extraction Of Small Boat Harmonic Signatures From Passive Sonar, George Lloyd Ogden, Lisa M. Zurk, M. E. Jones, M. E. Peterson
Electrical and Computer Engineering Faculty Publications and Presentations
This paper investigates the extraction of acoustic signatures from small boats using a passive sonar system. Noise radiated from a small boats consists of broadband noise and harmonically related tones that correspond to engine and propeller specifications. A signal processing method to automatically extract the harmonic structure of noise radiated from small boats is developed. The Harmonic Extraction and Analysis Tool (HEAT) estimates the instantaneous fundamental frequency of the harmonic tones, refines the fundamental frequency estimate using a Kalman filter, and automatically extracts the amplitudes of the harmonic tonals to generate a harmonic signature for the boat. Results are presented …
Adaptive Passive Fathometer Processing, Martin Siderius, Heechun Song, Peter Gerstoft, William S. Hodgkiss, Paul Hursky, Chris H. Harrison
Adaptive Passive Fathometer Processing, Martin Siderius, Heechun Song, Peter Gerstoft, William S. Hodgkiss, Paul Hursky, Chris H. Harrison
Electrical and Computer Engineering Faculty Publications and Presentations
Recently, a technique has been developed to image seabed layers using the ocean ambient noise field as the sound source. This so called passive fathometer technique exploits the naturally occurring acoustic sounds generated on the sea-surface, primarily from breaking waves. The method is based on the cross-correlation of noise from the ocean surface with its echo from the seabed, which recovers travel times to significant seabed reflectors. To limit averaging time and make this practical, beamforming is used with a vertical array of hydrophones to reduce interference from horizontally propagating noise. The initial development used conventional beamforming, but significant improvements …
Effects Of Sea-Surface Conditions On Passive Fathometry And Bottom Characterization, Steven L. Means, Martin Siderius
Effects Of Sea-Surface Conditions On Passive Fathometry And Bottom Characterization, Steven L. Means, Martin Siderius
Electrical and Computer Engineering Faculty Publications and Presentations
Recently, a method has been developed that exploits the correlation properties of the ocean’s ambient noise to measure water depth (a passive fathometer) and seabed layering [M. Sideriuset al., J. Acoust. Soc. Am.120, 1315–1323 (2006)]. This processing is based on the cross-correlation between the surface noise and the echo return from the seabed. To quantitatively study the dependency between processing and environmental factors such as wind speed, measurements were made using a fixed hydrophone array while simultaneously characterizing the environment. The measurements were made in 2006 in the shallow waters (25m)approximately 75km off the coast of Savannah, GA. …
Modeling Broadband Ocean Acoustic Transmissions With Time-Varying Sea Surfaces, Martin Siderius, Michael B. Porter
Modeling Broadband Ocean Acoustic Transmissions With Time-Varying Sea Surfaces, Martin Siderius, Michael B. Porter
Electrical and Computer Engineering Faculty Publications and Presentations
Solutions to ocean acoustic scattering problems are often formulated in the frequency domain, which implies that the surface is "frozen" in time. This may be reasonable for short duration signals but breaks down if the surface changes appreciably over the transmission time. Frequency domain solutions are also impractical for source-receiver ranges and frequency bands typical for applications such as acoustic communications (e.g. hundreds to thousands of meters, 1-50 kHz band). In addition, a driving factor in the performance of certain acoustic systems is the Doppler spread, which is often introduced from sea-surface movement. The time-varying nature of the sea surface …
Bottom Profiling By Correlating Beam-Steered Noise Sequences, Chris H. Harrison, Martin Siderius
Bottom Profiling By Correlating Beam-Steered Noise Sequences, Chris H. Harrison, Martin Siderius
Electrical and Computer Engineering Faculty Publications and Presentations
It has already been established that by cross-correlating ambient noisetime series received on the upward and downward steered beams of a drifting vertical array one can obtain a subbottom layer profile. Strictly, the time differential of the cross correlation is the impulse response of the seabed. Here it is shown theoretically and by simulation that completely uncorrelated surfacenoise results in a layer profile with predictable amplitudes proportional to those of an equivalent echo sounder at the same depth as the array. The phenomenon is simulated by representing the sound sources as multiple random time sequences emitted from random locations in …
Passive Fathometer Processing, Peter Gerstoft, William S. Hodgkiss, Martin Siderius, Chen-Fen Huang, Chris H. Harrison
Passive Fathometer Processing, Peter Gerstoft, William S. Hodgkiss, Martin Siderius, Chen-Fen Huang, Chris H. Harrison
Electrical and Computer Engineering Faculty Publications and Presentations
Ocean acoustic noise can be processed efficiently to extract Green's function information between two receivers. By using noise array-processing techniques, it has been demonstrated that a passive array can be used as a fathometer [Siderius, et al., J. Acoust. Soc. Am. 120, 1315-1323 (2006)]. Here, this approach is derived in both frequency and time domains and the output corresponds to the reflection sequence. From this reflection sequence, it is possible to extract seabed layering. In the ocean waveguide, most of the energy is horizontally propagating, whereas the bottom information is contained in the vertically propagating noise. Extracting the seabed information …
Source Localization In A Time-Varying Ocean Waveguide, Cristiano Soares, Martin Siderius, Sérgio M. Jesus
Source Localization In A Time-Varying Ocean Waveguide, Cristiano Soares, Martin Siderius, Sérgio M. Jesus
Electrical and Computer Engineering Faculty Publications and Presentations
One of the most stringent impairments in matched-field processing is the impact of missing or erroneous environmental information on the final source location estimate. This problem is known in the literature as model mismatch and is strongly frequency dependent. Another unavoidable factor that contributes to model mismatch is the natural time and spatial variability of the ocean waveguide. As a consequence, most of the experimental results obtained to date focus on short source-receiver ranges (usually <5 >km), stationary sources, reduced time windows and frequencies generally below 600 Hz. This paper shows that MFP source localization can be made robust to time–space …
Range-Dependent Seabed Characterization By Inversion Of Acoustic Data From A Towed Receiver Array, Martin Siderius, Peter L. Nielsen, Peter Gerstoft
Range-Dependent Seabed Characterization By Inversion Of Acoustic Data From A Towed Receiver Array, Martin Siderius, Peter L. Nielsen, Peter Gerstoft
Electrical and Computer Engineering Faculty Publications and Presentations
The MAPEX2000 experiments were conducted in the Mediterranean Sea in March, 2000 to determine seabed properties using a towed acoustic source and receiver array. Towed systems are advantageous because they are easy to deploy from a ship and the moving platform offers the possibility for estimating spatially variable (range-dependent) seabed properties. In this paper, seabed parameters are determined using a matched-field geoacoustic inversion approach with measured, towed array data. Previous research has successfully applied matched-field geoacoustic inversion techniques to measured acoustic data. However, in nearly all cases the inverted data were collected on moored, vertical receiver arrays. Results here show …