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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.
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 …
Marine Mammal Tracks From Two-Hydrophone Acoustic Recordings Made With A Glider, Elizabeth T. Küsel, Tessa Munoz, Martin Siderius, David K. Mellinger, Sara L. Heimlich
Marine Mammal Tracks From Two-Hydrophone Acoustic Recordings Made With A Glider, Elizabeth T. Küsel, Tessa Munoz, Martin Siderius, David K. Mellinger, Sara L. Heimlich
Electrical and Computer Engineering Faculty Publications and Presentations
A multinational oceanographic and acoustic sea experiment was carried out in the summer of 2014 off the western coast of the island of Sardinia, Mediterranean Sea. During this experiment, an underwater glider fitted with two hydrophones was evaluated as a potential tool for marine mammal population density estimation studies. An acoustic recording system was also tested, comprising an inexpensive, off-the-shelf digital recorder installed inside the glider. Detection and classification of sounds produced by whales and dolphins, and sometimes tracking and localization, are inherent components of population density estimation from passive acoustics recordings. In this work we discuss the equipment used …
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.
A Computational Method To Predict And Study Underwater Noise Due To Pile Driving, Scott Schecklman, Nathan Laws, Lisa M. Zurk, Martin Siderius
A Computational Method To Predict And Study Underwater Noise Due To Pile Driving, Scott Schecklman, Nathan Laws, Lisa M. Zurk, Martin Siderius
Electrical and Computer Engineering Faculty Publications and Presentations
A hybrid modeling approach that uses the parabolic equation (PE) with an empirical source model is presented to study and predict the underwater noise due to pile driving in shallow, inhomogeneous environments over long propagation ranges. The empirical source model uses a phased point source array to simulate the time-dependent pile source. The pile source is coupled with a broadband application of a PE wave propagation model that includes range dependent geoacoustic properties and bathymetry. Simulation results are shown to be in good agreement with several acoustic observations of pile driving in the Columbia River between Portland, OR and Vancouver, …
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.
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 …
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 …