The Journal of the Acoustical Society of America, 2002
Measurements of acoustic forward and backscattering have been made by DRDC Atlantic during collab... more Measurements of acoustic forward and backscattering have been made by DRDC Atlantic during collaborative sea-trials on the Scotian Shelf off the coast of Nova Scotia and on the Strataform site off the coast of New Jersey. In this paper, the geoacoustic properties and roughness parameters that are necessary to interpret and model the scattering measurements are presented. They have been determined using complementary in situ and acoustic techniques. The in situ measurements have been made using grab samples and a free fall cone penetrometer that has been fitted with a resistivity module. The probe provides two independent means of calculating the undrained shear strength, an empirical sediment classification and sediment bulk density. The acoustic measurements include inversions for geoacoustic parameters using the WARBLE [Holland and Osler, J. Acoust. Soc. Am. (2000)] and normal incidence sediment classification [Hines and Heald, Proc. Inst. Acoust. (2001)] techniques. At the scattering experimental locations, these measurements have been combined with surveys using commercial equipment: sidescan sonar, multibeam bathymetry, and subbottom profilers to characterize the seabed.
The Journal of the Acoustical Society of America, 2013
ABSTRACT Buoyancy-driven underwater gliders are autonomous underwater vehicles that were original... more ABSTRACT Buoyancy-driven underwater gliders are autonomous underwater vehicles that were originally developed to collect oceanographic data. CMRE is studying the use of this technology for the characterization of denied areas, including alternate sensor payloads and applications. During the Rapid Environmental Assessment phase of the Noble Mariner 2012 NATO exercise, Conducted in Gulf of Lions in September 2012, an omnidirectional hydrophone was mounted on a shallow water glider to sample the spatial distribution of the acoustic and oceanographic fields at different ranges and depths. This paper presents a study of the potential to localize acoustic sources by using the acoustic and environmental data collected by the glider. During the experiment, a bottom moored acoustic source was deployed in an area with benign bathymetry. Continuous wave and frequency modulated pulses were broadcast for approximately 6 h. The glider was flying along predefined tracks and the distances from the source were typically from 5 to 9 km. A Ray tracing model is used to evaluate the arrival structures of the acoustic signal, and to estimate the source location. The impact of the range dependent water column sound speed profile on the uncertainty of the source localization is also discussed.
The Journal of the Acoustical Society of America, Jun 1, 2005
Direct measurement of acoustic scattering from the seabed at shallow grazing angles and low kiloh... more Direct measurement of acoustic scattering from the seabed at shallow grazing angles and low kilohertz frequencies presents a considerable challenge in littoral waters. Specifically, returns from the air-water interface typically contaminate the signals of interest. To address this issue, DRDC Atlantic has developed a sea-going research system for measuring acoustic scatter from the seabed in shallow-water environs. The system, known as the wideband sonar (WBS), consists of a parametric array transmitter and a superdirective receiver. In this paper, backscatter measurements obtained with the WBS at two sandy, shallow-water sites off North America's Atlantic coast are presented. Data were collected at 4 and 8 kHz at grazing angles from 3°-15°. The backscattering strength is similar at both sites and, below about 8°, it appears to be independent of frequency within the statistical accuracy of the data. The measurements show reasonable agreement with model estimates of backscatter from sandy sediments. A small data set was collected at one of the sites to examine the feasibility of using the WBS to measure the azimuthal variability of acoustic scatter. The data set-although limited-indicates that the parametric array's narrow beamwidth makes the system well-suited to this task. .
... The authors wish to thank the officers and the crew of CFAV Quest and CCGS Matthew for their ... more ... The authors wish to thank the officers and the crew of CFAV Quest and CCGS Matthew for their assistance during sea trials. ... 1. Furlong, A., Bugden, G., Beanlands, B., Eisan, M, Suguro, K, Namiki, Y., Near vertical water column in-situ profiling with a Moving Vessel Profiler (MVP ...
The Journal of the Acoustical Society of America, 2002
Measurements of acoustic forward and backscattering have been made by DRDC Atlantic during collab... more Measurements of acoustic forward and backscattering have been made by DRDC Atlantic during collaborative sea-trials on the Scotian Shelf off the coast of Nova Scotia and on the Strataform site off the coast of New Jersey. In this paper, the geoacoustic properties and roughness parameters that are necessary to interpret and model the scattering measurements are presented. They have been determined using complementary in situ and acoustic techniques. The in situ measurements have been made using grab samples and a free fall cone penetrometer that has been fitted with a resistivity module. The probe provides two independent means of calculating the undrained shear strength, an empirical sediment classification and sediment bulk density. The acoustic measurements include inversions for geoacoustic parameters using the WARBLE [Holland and Osler, J. Acoust. Soc. Am. (2000)] and normal incidence sediment classification [Hines and Heald, Proc. Inst. Acoust. (2001)] techniques. At the scattering experimental locations, these measurements have been combined with surveys using commercial equipment: sidescan sonar, multibeam bathymetry, and subbottom profilers to characterize the seabed.
The Journal of the Acoustical Society of America, 2013
ABSTRACT Buoyancy-driven underwater gliders are autonomous underwater vehicles that were original... more ABSTRACT Buoyancy-driven underwater gliders are autonomous underwater vehicles that were originally developed to collect oceanographic data. CMRE is studying the use of this technology for the characterization of denied areas, including alternate sensor payloads and applications. During the Rapid Environmental Assessment phase of the Noble Mariner 2012 NATO exercise, Conducted in Gulf of Lions in September 2012, an omnidirectional hydrophone was mounted on a shallow water glider to sample the spatial distribution of the acoustic and oceanographic fields at different ranges and depths. This paper presents a study of the potential to localize acoustic sources by using the acoustic and environmental data collected by the glider. During the experiment, a bottom moored acoustic source was deployed in an area with benign bathymetry. Continuous wave and frequency modulated pulses were broadcast for approximately 6 h. The glider was flying along predefined tracks and the distances from the source were typically from 5 to 9 km. A Ray tracing model is used to evaluate the arrival structures of the acoustic signal, and to estimate the source location. The impact of the range dependent water column sound speed profile on the uncertainty of the source localization is also discussed.
The Journal of the Acoustical Society of America, Jun 1, 2005
Direct measurement of acoustic scattering from the seabed at shallow grazing angles and low kiloh... more Direct measurement of acoustic scattering from the seabed at shallow grazing angles and low kilohertz frequencies presents a considerable challenge in littoral waters. Specifically, returns from the air-water interface typically contaminate the signals of interest. To address this issue, DRDC Atlantic has developed a sea-going research system for measuring acoustic scatter from the seabed in shallow-water environs. The system, known as the wideband sonar (WBS), consists of a parametric array transmitter and a superdirective receiver. In this paper, backscatter measurements obtained with the WBS at two sandy, shallow-water sites off North America's Atlantic coast are presented. Data were collected at 4 and 8 kHz at grazing angles from 3°-15°. The backscattering strength is similar at both sites and, below about 8°, it appears to be independent of frequency within the statistical accuracy of the data. The measurements show reasonable agreement with model estimates of backscatter from sandy sediments. A small data set was collected at one of the sites to examine the feasibility of using the WBS to measure the azimuthal variability of acoustic scatter. The data set-although limited-indicates that the parametric array's narrow beamwidth makes the system well-suited to this task. .
... The authors wish to thank the officers and the crew of CFAV Quest and CCGS Matthew for their ... more ... The authors wish to thank the officers and the crew of CFAV Quest and CCGS Matthew for their assistance during sea trials. ... 1. Furlong, A., Bugden, G., Beanlands, B., Eisan, M, Suguro, K, Namiki, Y., Near vertical water column in-situ profiling with a Moving Vessel Profiler (MVP ...
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Papers by John Osler