摘要 :
The long term goal is to improve performance of low-mid frequency active sonar systems operating in littoral regions. One of the most serious problems for employment of active sonars is the overwhelming number of clutter events, m...
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The long term goal is to improve performance of low-mid frequency active sonar systems operating in littoral regions. One of the most serious problems for employment of active sonars is the overwhelming number of clutter events, many of which come from geologic features on and in the seabed.
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摘要 :
The long term science goal is to understand the specific seabed mechanisms that control clutter and diffuse reverberation. The specific goals are to: (1) quantify seabed physical properties and their spatial (vertical and horizont...
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The long term science goal is to understand the specific seabed mechanisms that control clutter and diffuse reverberation. The specific goals are to: (1) quantify seabed physical properties and their spatial (vertical and horizontal) variability and uncertainties and (2) make and test hypotheses about the mechanisms that control clutter and diffuse reverberation.
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The long term goals of this program are to develop normal incidence FM acoustic reflection techniques for remotely measuring the physical and acoustic properties of ocean sediments and to improve our understanding of seabed acoustics.
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The long-term science question addressed by the SW2013 experiment (relevant to this proposal) is to advance understanding of the seabed mechanisms that control clutter and diffuse reverberation. The specific goals are to: 1) quant...
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The long-term science question addressed by the SW2013 experiment (relevant to this proposal) is to advance understanding of the seabed mechanisms that control clutter and diffuse reverberation. The specific goals are to: 1) quantify seabed physical properties and their spatial (vertical and horizontal) variability and uncertainties and 2) based on the spatial variability make and test hypotheses about the mechanisms that control clutter and diffuse reverberation.
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This report evaluates the effectiveness of the Biot-Stoll model of a poroelastic seabed in predicting experimentally observed phenomena in underwater acoustics. Discussed in the report is the derivation of the model from physical ...
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This report evaluates the effectiveness of the Biot-Stoll model of a poroelastic seabed in predicting experimentally observed phenomena in underwater acoustics. Discussed in the report is the derivation of the model from physical principles, including more recent extensions such as the distributed pore size formulation of Turgut and Yamamoto and a more sophisticated approach to modeling intergranular effects advocated by Chotiros and Isakson. It is found that with the incorporation of these two extensions, the Biot-Stoll model is capable of producing good agreement with experimentally measured values of compressional wave speed and attenuation. It should be noted however, that there are not currently efficacious ways of measuring the new parameters introduced by these extensions other than adjusting them to wave speed and attenuation data measured over multiple decades of frequency. Also discussed in the report are the determination of the Biot-Stoll parameters, reflection and transmission at the ocean sediment surface, models for depth- varying sediment properties and some of the difficulties with, and controversies concerning, the Biot-Stoll model.
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The long-term goals of this work are: to develop a theoretical model for predicting the reverberation in shallow water, to derive both small-angle seabed reflectivity and scattering strength from reverberation data at low frequenc...
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The long-term goals of this work are: to develop a theoretical model for predicting the reverberation in shallow water, to derive both small-angle seabed reflectivity and scattering strength from reverberation data at low frequency, and to understand the physical mechanism of sea bottom scattering. The scientific objective of this research is to investigate the effects of the sea bottom on sound propagation, reverberation and signal coherence in shallow water for a frequency range of 100 Hz-3000 Hz. Our specific objectives are (I) to simultaneously measure acoustic data and geologic and geophysical data at carefully chosen sea areas. (II) to derive sound velocity and attenuation in sediments from sound propagation. And (III) to characterize the seabottom scattering function from reverberation measurements.
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摘要 :
The long term research objective is to develop a cost effective technique for mapping the top 20 meters of sediment properties using acoustic remote sensing. In previous years, a chirp sonar was developed to provide quantitative, ...
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The long term research objective is to develop a cost effective technique for mapping the top 20 meters of sediment properties using acoustic remote sensing. In previous years, a chirp sonar was developed to provide quantitative, wideband reflection measurements of the seabed with a vertical resolution of 10 cm. Neural network and fuzzy logic techniques have been used to automatically detect subsurface layer interfaces and to find the boundaries between sediment layers. Signal processing techniques were developed to estimate vertical profiles of impedance and attenuation. The procedures for remotely estimating sediment properties are being verified using core data and in situ measurements. New signal processing techniques have been developed that allow several sources transmitting simultaneously in different bands to build a wideband FM pulse in the far field. That wideband data is being used to improve the accuracy of the sediment classification procedures and to provide the capability of measuring phase dispersion.
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摘要 :
The long term research objective is to develop a cost effective technique for mapping the top 20 meters of sediment properties using acoustic remote sensing. In previous years, a chirp sonar was developed to provide quantitative, ...
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The long term research objective is to develop a cost effective technique for mapping the top 20 meters of sediment properties using acoustic remote sensing. In previous years, a chirp sonar was developed to provide quantitative, wideband reflection measurements of the seabed with a vertical resolution of 10 cm. Fuzzy logic techniques have been used to automatically detect subsurface layer interfaces and to find the boundaries between sediment layers. Signal processing techniques were developed to estimate vertical profiles of impedance and attenuation. The procedures for remotely estimating sediment properties are being verified using core data and insitu measurements. New signal processing techniques have been developed that allow several sources transmitting simultaneously in different bands to build a wideband FM pulse in the far field. That wideband data is being used to improve the accuracy of the measuring sediment properties including impedance, attenuation and phase dispersion.
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