The chirp sonar--a high-resolution, quantitative subbottom profiler
The chirp sonar is a quantitative subbottom profiler that can generate wide dynamic range, artifact-free seismograms in real time. These high quality seismograms, can be used for quantitative analyses, such as reflectivity and attenuation measurements, and sediment classification. Key features of th...
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ftunivrhodeislan:oai:digitalcommons.uri.edu:dissertations-1235 2023-05-15T16:34:50+02:00 The chirp sonar--a high-resolution, quantitative subbottom profiler Schock, Steven Gregory 1989-01-01T08:00:00Z https://digitalcommons.uri.edu/dissertations/AAI9008849 ENG eng DigitalCommons@URI https://digitalcommons.uri.edu/dissertations/AAI9008849 Dissertations and Master's Theses (Campus Access) Ocean engineering|Electrical engineering|Acoustics|Remote sensing text 1989 ftunivrhodeislan 2021-06-29T19:14:13Z The chirp sonar is a quantitative subbottom profiler that can generate wide dynamic range, artifact-free seismograms in real time. These high quality seismograms, can be used for quantitative analyses, such as reflectivity and attenuation measurements, and sediment classification. Key features of the chirp sonar include (1) a computer-generated FM pilot signal with a large time-bandwidth product that contains amplitude and phase compensation providing exact control of the transmitted acoustic pulse (2) directional arrays with low backlobe levels and (3) a towed vehicle designed to scatter bottom multiples. Subbottom profiles, acquired in Narragansett Bay, R.I., demonstrated 20 cm vertical resolution, 62 meter subbottom penetration and significant bottom multiple reduction. A new time domain technique for estimating acoustic attenuation, called the autocorrelation method, is described and compared to well known attenuation measurement techniques. The spectral ratio method is most accurate, followed by the autocorrelation and wavelet matching methods for estimating the acoustic attenuation coefficient of sediments from reflection profiles. However, the autocorrelation method is the only technique efficient enough to provide an attenuation measurement for every depth increment in each acoustic return in real time. Multiple reflections, gradual impedance changes and windowing sidelobes degrade the attenuation estimates. Chirp sonar remote measurements off Hope Island were used to estimate the attenuation coefficient for clayey silts (0.091 dB/m/kHz by spectral ratio and 0.125 dB/m/kHz by autocorrelation), values which agree with in situ measurements made by Hamilton, but are significantly higher than the attenuation coefficient (0.019 dB/m/kHz, n = 1.50) calculated from laboratory measurements (250-750 kHz) on a core from the Hope Island site. More ground truth measurements are required to establish the accuracy of remote attenuation measurements using the chirp sonar. Text Hope island University of Rhode Island: DigitalCommons@URI Hope Island ENVELOPE(-56.849,-56.849,-63.033,-63.033) |
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collection |
University of Rhode Island: DigitalCommons@URI |
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ftunivrhodeislan |
language |
English |
topic |
Ocean engineering|Electrical engineering|Acoustics|Remote sensing |
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Ocean engineering|Electrical engineering|Acoustics|Remote sensing Schock, Steven Gregory The chirp sonar--a high-resolution, quantitative subbottom profiler |
topic_facet |
Ocean engineering|Electrical engineering|Acoustics|Remote sensing |
description |
The chirp sonar is a quantitative subbottom profiler that can generate wide dynamic range, artifact-free seismograms in real time. These high quality seismograms, can be used for quantitative analyses, such as reflectivity and attenuation measurements, and sediment classification. Key features of the chirp sonar include (1) a computer-generated FM pilot signal with a large time-bandwidth product that contains amplitude and phase compensation providing exact control of the transmitted acoustic pulse (2) directional arrays with low backlobe levels and (3) a towed vehicle designed to scatter bottom multiples. Subbottom profiles, acquired in Narragansett Bay, R.I., demonstrated 20 cm vertical resolution, 62 meter subbottom penetration and significant bottom multiple reduction. A new time domain technique for estimating acoustic attenuation, called the autocorrelation method, is described and compared to well known attenuation measurement techniques. The spectral ratio method is most accurate, followed by the autocorrelation and wavelet matching methods for estimating the acoustic attenuation coefficient of sediments from reflection profiles. However, the autocorrelation method is the only technique efficient enough to provide an attenuation measurement for every depth increment in each acoustic return in real time. Multiple reflections, gradual impedance changes and windowing sidelobes degrade the attenuation estimates. Chirp sonar remote measurements off Hope Island were used to estimate the attenuation coefficient for clayey silts (0.091 dB/m/kHz by spectral ratio and 0.125 dB/m/kHz by autocorrelation), values which agree with in situ measurements made by Hamilton, but are significantly higher than the attenuation coefficient (0.019 dB/m/kHz, n = 1.50) calculated from laboratory measurements (250-750 kHz) on a core from the Hope Island site. More ground truth measurements are required to establish the accuracy of remote attenuation measurements using the chirp sonar. |
format |
Text |
author |
Schock, Steven Gregory |
author_facet |
Schock, Steven Gregory |
author_sort |
Schock, Steven Gregory |
title |
The chirp sonar--a high-resolution, quantitative subbottom profiler |
title_short |
The chirp sonar--a high-resolution, quantitative subbottom profiler |
title_full |
The chirp sonar--a high-resolution, quantitative subbottom profiler |
title_fullStr |
The chirp sonar--a high-resolution, quantitative subbottom profiler |
title_full_unstemmed |
The chirp sonar--a high-resolution, quantitative subbottom profiler |
title_sort |
chirp sonar--a high-resolution, quantitative subbottom profiler |
publisher |
DigitalCommons@URI |
publishDate |
1989 |
url |
https://digitalcommons.uri.edu/dissertations/AAI9008849 |
long_lat |
ENVELOPE(-56.849,-56.849,-63.033,-63.033) |
geographic |
Hope Island |
geographic_facet |
Hope Island |
genre |
Hope island |
genre_facet |
Hope island |
op_source |
Dissertations and Master's Theses (Campus Access) |
op_relation |
https://digitalcommons.uri.edu/dissertations/AAI9008849 |
_version_ |
1766024875052367872 |