Search

Search Results

• 1. [Article] Head Wave Correlations in Ambient Noise

  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 ...

  Citation × Citation Citation Abstract Copy Title: Head Wave Correlations in Ambient Noise Author: Gebbie, John Thomas, Siderius, Martin Year: 2016 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. Title: Head Wave Correlations in Ambient Noise Author: Gebbie, John Thomas, Siderius, Martin Year: 2016 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. Close

• 2. [Article] Glider-based Seabed Characterization using Natural-made Ambient Noise

  Seabed characteristics (geoacoustic properties and scattering strength) are critical parameters for sonar performance predictions. However, this bottom information is considered very difficult and expensive ...

  Citation × Citation Citation Abstract Copy Title: Glider-based Seabed Characterization using Natural-made Ambient Noise Author: Nielsen, Peter L., Siderius, Martin, Muzi, Lanfranco Year: 2015 Seabed characteristics (geoacoustic properties and scattering strength) are critical parameters for sonar performance predictions. However, this bottom information is considered very difficult and expensive to achieve in the scientific community. In this report, an efficient method for inferring the seabed properties is presented; it relies on a previous methodology using long moored or drifting hydrophone arrays. Results from sea trials demonstrate the feasibility of using the technique by deploying a hybrid autonomous underwater vehicle hosting a unique hydrophone array consisting of a five-element vertical line array and a four-element tetrahedral array. Seabed reflection and layering properties are estimated from sea surface generated ambient noise acquired during two trials in different shallow-water areas. Results from numerical modeling, data analysis and experimental measurements are presented with emphasis on comparing the seabed characterization at different locations with different bottom properties. The results obtained from both experiments demonstrate the potential of using autonomous underwater vehicles for seabed characterization and surface vessel tracking. Title: Glider-based Seabed Characterization using Natural-made Ambient Noise Author: Nielsen, Peter L., Siderius, Martin, Muzi, Lanfranco Year: 2015 Seabed characteristics (geoacoustic properties and scattering strength) are critical parameters for sonar performance predictions. However, this bottom information is considered very difficult and expensive to achieve in the scientific community. In this report, an efficient method for inferring the seabed properties is presented; it relies on a previous methodology using long moored or drifting hydrophone arrays. Results from sea trials demonstrate the feasibility of using the technique by deploying a hybrid autonomous underwater vehicle hosting a unique hydrophone array consisting of a five-element vertical line array and a four-element tetrahedral array. Seabed reflection and layering properties are estimated from sea surface generated ambient noise acquired during two trials in different shallow-water areas. Results from numerical modeling, data analysis and experimental measurements are presented with emphasis on comparing the seabed characterization at different locations with different bottom properties. The results obtained from both experiments demonstrate the potential of using autonomous underwater vehicles for seabed characterization and surface vessel tracking. Close

• 3. [Article] Passive Acoustical Oceanography

  Acoustical Oceanography includes the use of both active and passive acoustic systems to measure various properties of the ocean environment. Active methods use a specifically designed and controlled sound ...

  Citation × Citation Citation Abstract Copy Title: Passive Acoustical Oceanography Author: Siderius, Martin Year: 2016 Acoustical Oceanography includes the use of both active and passive acoustic systems to measure various properties of the ocean environment. Active methods use a specifically designed and controlled sound projector while passive methods exploit naturally occurring ocean sounds such as breaking waves, ship noise, or marine mammal vocalizations. Historically, active methods have been the preferred choice when precise propagation times or calibrated sound levels are important. However, passive sensing has a strong appeal due in part to the ease in which listening-only systems can be deployed. There have been a number of advances in passive sensing even for cases where propagation times and sound levels are of interest. For example, it has been shown that surface wave noise can be used to measure vertical propagation times through the seabed and water column. More recently, there is experimental evidence that indicates noise correlations may also be used to determine horizontal propagation times in the seabed. Although replacing controlled projectors with noise sources is an attractive option there are limitations to how and when noise can be used this way. These limitations as well as experimental and modeling results from surface and ship noise will be described in this presentation. Title: Passive Acoustical Oceanography Author: Siderius, Martin Year: 2016 Acoustical Oceanography includes the use of both active and passive acoustic systems to measure various properties of the ocean environment. Active methods use a specifically designed and controlled sound projector while passive methods exploit naturally occurring ocean sounds such as breaking waves, ship noise, or marine mammal vocalizations. Historically, active methods have been the preferred choice when precise propagation times or calibrated sound levels are important. However, passive sensing has a strong appeal due in part to the ease in which listening-only systems can be deployed. There have been a number of advances in passive sensing even for cases where propagation times and sound levels are of interest. For example, it has been shown that surface wave noise can be used to measure vertical propagation times through the seabed and water column. More recently, there is experimental evidence that indicates noise correlations may also be used to determine horizontal propagation times in the seabed. Although replacing controlled projectors with noise sources is an attractive option there are limitations to how and when noise can be used this way. These limitations as well as experimental and modeling results from surface and ship noise will be described in this presentation. Close

• 4. [Article] A Two-hydrophone Range and Bearing Localization with Performance Analysis

  An automated, passive algorithm for detecting and localizing small boats using two hydrophones mounted on the seabed is outlined. This extends previous work by Gebbie et al. [(2013). J. Acoust. Soc. Am. ...

  Citation × Citation Citation Abstract Copy Title: A Two-hydrophone Range and Bearing Localization with Performance Analysis Author: Gebbie, John Thomas, Siderius, Martin, Allen, John S., III Year: 2015 An automated, passive algorithm for detecting and localizing small boats using two hydrophones mounted on the seabed is outlined. This extends previous work by Gebbie et al. [(2013). J. Acoust. Soc. Am. 134, EL77 − EL83] in which a similar two-hydrophone approach is used to produce an ambiguity surface of likely target locations leveraging multipath analysis and knowledge of the local bathymetry. The work presented here improves upon the prior approach using particle filtering to automate detection and localization processing. A detailed analysis has also been conducted to determine the conditions and limits under which the improved approach can be expected to yield accurate range and unambiguous bearing information. Experimental results in 12 m of water allow for a comparison of different separation distances between hydrophones, and the Bayesian Cramér-Rao lower bound is used to extrapolate the performance expected in 120 m water. This work demonstrates the conditions under which a low cost, passive, sparse array of hydrophones can provide a meaningful small boat detection and localization capability. Title: A Two-hydrophone Range and Bearing Localization with Performance Analysis Author: Gebbie, John Thomas, Siderius, Martin, Allen, John S., III Year: 2015 An automated, passive algorithm for detecting and localizing small boats using two hydrophones mounted on the seabed is outlined. This extends previous work by Gebbie et al. [(2013). J. Acoust. Soc. Am. 134, EL77 − EL83] in which a similar two-hydrophone approach is used to produce an ambiguity surface of likely target locations leveraging multipath analysis and knowledge of the local bathymetry. The work presented here improves upon the prior approach using particle filtering to automate detection and localization processing. A detailed analysis has also been conducted to determine the conditions and limits under which the improved approach can be expected to yield accurate range and unambiguous bearing information. Experimental results in 12 m of water allow for a comparison of different separation distances between hydrophones, and the Bayesian Cramér-Rao lower bound is used to extrapolate the performance expected in 120 m water. This work demonstrates the conditions under which a low cost, passive, sparse array of hydrophones can provide a meaningful small boat detection and localization capability. Close

• 5. [Article] Frequency Based Noise Coherence-Function Extension and Application to Passive Bottom-Loss Estimation

  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 ...

  Citation × Citation Citation Abstract Copy Title: Frequency Based Noise Coherence-Function Extension and Application to Passive Bottom-Loss Estimation Author: Muzi, Lanfranco, Siderius, Martin, Nielsen, Peter L. Year: 2016 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 0px; margin: 0px; position: relative;">10 kHz10 kHz It is shown in this paper that, when the data are free of interference from sources other than wind and wave surface noise, data from a shorter array can be used to approximate the coherence function of a longer array. This improves the angular resolution of the estimated bottom loss, often making use of data at frequencies above the array design frequency. Application to simulated and experimental data shows that the technique, rigorously justified for a halfspace bottom, is effective also on more complex bottom types. Dispensing with active sources, small autonomous underwater vehicles equipped with short arrays can be envisioned as compact, efficient seabed-characterization systems. The proposed technique is shown to improve significantly the reflection-loss estimate of an array that would be a candidate for such application. Title: Frequency Based Noise Coherence-Function Extension and Application to Passive Bottom-Loss Estimation Author: Muzi, Lanfranco, Siderius, Martin, Nielsen, Peter L. Year: 2016 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 0px; margin: 0px; position: relative;">10 kHz10 kHz It is shown in this paper that, when the data are free of interference from sources other than wind and wave surface noise, data from a shorter array can be used to approximate the coherence function of a longer array. This improves the angular resolution of the estimated bottom loss, often making use of data at frequencies above the array design frequency. Application to simulated and experimental data shows that the technique, rigorously justified for a halfspace bottom, is effective also on more complex bottom types. Dispensing with active sources, small autonomous underwater vehicles equipped with short arrays can be envisioned as compact, efficient seabed-characterization systems. The proposed technique is shown to improve significantly the reflection-loss estimate of an array that would be a candidate for such application. Close