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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.
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.
Passive Localization Of Noise-Producing Targets Using A Compact Volumetric Array, John Gebbie, Martin Siderius, Peter L. Nielsen, James Miller
Passive Localization Of Noise-Producing Targets Using A Compact Volumetric Array, John Gebbie, Martin Siderius, Peter L. Nielsen, James Miller
Electrical and Computer Engineering Faculty Publications and Presentations
A technique is presented for passively localizing multiple noise-producing targets by cross-correlating the elevation beams of a compact volumetric array on separate bearings. A target’s multipath structure inherently contains information about its range; however, unknown, random noise waveforms make time separation of individual arrivals difficult. Ocean ambient noise has previously been used to measure multipath delays to the seabed by cross-correlating the beams of a vertical line array [Siderius, Song, Gerstoft, Hodgkiss, Hursky, and Harrison, J. Acoust. Soc. Am. 127, 2193–2200 (2010)], but this methodology has not been applied to distant noise sources having non-vertical arrivals. The technique presented in …
Aspect-Dependent Radiated Noise Analysis Of An Underway Autonomous Underwater Vehicle, John Gebbie, Martin Siderius, John S. Allen Iii
Aspect-Dependent Radiated Noise Analysis Of An Underway Autonomous Underwater Vehicle, John Gebbie, Martin Siderius, John S. Allen Iii
Electrical and Computer Engineering Faculty Publications and Presentations
This paper presents an analysis of the acoustic emissions emitted by an underway REMUS-100 autonomous underwater vehicle(AUV) that were obtained near Honolulu Harbor, HI using a fixed, bottom-mounted horizontal line array (HLA). Spectral analysis,beamforming, and cross-correlation facilitate identification of independent sources of noise originating from the AUV. Fusion of navigational records from the AUV with acoustic data from the HLA allows for an aspect-dependent presentation of calculated source levels of the strongest propulsion tone.
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 Ocean Thermocline Variability On Noncoherent Underwater Acoustic Communications, Martin Siderius, Michael B. Porter, Paul Hursky, Vincent Mcdonald
Effects Of Ocean Thermocline Variability On Noncoherent Underwater Acoustic Communications, Martin Siderius, Michael B. Porter, Paul Hursky, Vincent Mcdonald
Electrical and Computer Engineering Faculty Publications and Presentations
The performance of acoustic modems in the ocean is strongly affected by the oceanenvironment. A storm can drive up the ambient noise levels, eliminate a thermocline by wind mixing, and whip up violent waves and thereby break up the acoustic mirror formed by theocean surface. The combined effects of these and other processes on modem performance are not well understood. The authors have been conducting experiments to study these environmental effects on various modulation schemes. Here the focus is on the role of the thermocline on a widely used modulation scheme (frequency-shift keying). Using data from a recent experiment conducted …
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 …