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Full-Text Articles in Engineering
Comparison Of Conventional And Adaptive Acoustic Beamforming Algorithms Using A Tetrahedral Microphone Array In Noisy Environments, Megan Brittany Ewers
Comparison Of Conventional And Adaptive Acoustic Beamforming Algorithms Using A Tetrahedral Microphone Array In Noisy Environments, Megan Brittany Ewers
Dissertations and Theses
In situ acoustic measurements are often plagued by interfering sound sources that occur within the measurement environment. Both adaptive and conventional beamforming algorithms, when applied to the outputs of a microphone array arranged in a tetrahedral geometry, are able to capture sound sources in desired directions and reject sound from unwanted directions. Adaptive algorithms may be able to measure a desired sound source with greater spatial precision, but require more calculations and, therefore, computational power. A conventional frequency-domain phase-shift algorithm and a modified adaptive frequency-domain Minimum Variance Distortionless Response (MVDR) algorithm were applied to simulated and recorded signals from a …
Head Waves In Ocean Acoustic Ambient Noise: Measurements And Modeling, Martin Siderius, Jie Li, Peter Gerstoft
Head Waves In Ocean Acoustic Ambient Noise: Measurements And Modeling, Martin Siderius, Jie Li, Peter Gerstoft
Electrical and Computer Engineering Faculty Publications and Presentations
Seismic interferometry recovers the Green’s function between two receivers by cross-correlating the field measured from sources that surround the receivers. In the seismic literature, it has been widely reported that this processing can produce artifacts in the Green’s function estimate called “spurious multiples” or the “virtual refracted wave.” The spurious multiples are attributed to the head wave and its multiples and travels in the seabed. The head wave phenomenon is shown to be observable from both controlled active sources and from ocean ambient noise and for both vertical and horizontal arrays. The processing used is a generalization of the passive …
Passive Bottom Reflection-Loss Estimation Using Ship Noise And A Vertical Line Array, Lanfranco Muzi, Martin Siderius, Christopher M. Verlinden
Passive Bottom Reflection-Loss Estimation Using Ship Noise And A Vertical Line Array, Lanfranco Muzi, Martin Siderius, Christopher M. Verlinden
Electrical and Computer Engineering Faculty Publications and Presentations
An existing technique for passive bottom-loss estimation from natural marine surface noise (generated by waves and wind) is adapted to use noise generated by ships. The original approach—based on beamforming of the noise field recorded by a vertical line array of hydrophones—is retained; however, additional processing is needed in order for the field generated by a passing ship to show features that are similar to those of the natural surface-noise field. A necessary requisite is that the ship position, relative to the array, varies over as wide a range of steering angles as possible, ideally passing directly over the array …
Advances In Autonomous-Underwater-Vehicle Based Passive Bottom-Loss Estimation By Processing Of Marine Ambient Noise, Lanfranco Muzi
Advances In Autonomous-Underwater-Vehicle Based Passive Bottom-Loss Estimation By Processing Of Marine Ambient Noise, Lanfranco Muzi
Dissertations and Theses
Accurate modeling of acoustic propagation in the ocean waveguide is important to SONAR-performance prediction, and requires, particularly in shallow water environments, characterizing the bottom reflection loss with a precision that databank-based modeling cannot achieve. Recent advances in the technology of autonomous underwater vehicles (AUV) make it possible to envision a survey system for seabed characterization composed of a short array mounted on a small AUV. The bottom power reflection coefficient (and the related reflection loss) can be estimated passively by beamforming the naturally occurring marine ambient-noise acoustic field recorded by a vertical line array of hydrophones. However, the reduced array …
Eigenvector Pruning Method For High Resolution Beamforming, Jorge E. Quijano, Lisa M. Zurk
Eigenvector Pruning Method For High Resolution Beamforming, Jorge E. Quijano, Lisa M. Zurk
Electrical and Computer Engineering Faculty Publications and Presentations
This paper introduces an eigenvector pruning algorithm for the estimation of the signal-plus-interference eigenspace, required as a preliminary step to subspace beamforming. The proposed method considers large-aperture passive array configurations operating in environments with multiple maneuvering targets in background noise, in which the available data for estimation of sample covariances and eigenvectors are limited. Based on statistical properties of scalar products between deterministic and complex random vectors, this work defines a statistically justified threshold to identify target-related features embedded in the sample eigenvectors, leading to an estimator for the signal-bearing eigenspace. It is shown that data projection into this signal …
Advances In Aquatic Target Localization With Passive Sonar, John Thomas Gebbie
Advances In Aquatic Target Localization With Passive Sonar, John Thomas Gebbie
Dissertations and Theses
New underwater passive sonar techniques are developed for enhancing target localization capabilities in shallow ocean environments. The ocean surface and the seabed act as acoustic mirrors that reflect sound created by boats or subsurface vehicles, which gives rise to echoes that can be heard by hydrophone receivers (underwater microphones). The goal of this work is to leverage this "multipath" phenomenon in new ways to determine the origin of the sound, and thus the location of the target. However, this is difficult for propeller driven vehicles because the noise they produce is both random and continuous in time, which complicates its …