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Acoustic normal mode fluctuation statistics in the 1995 SWARM internal wave scattering experiment
The Journal of the Acoustical Society of America
|January 21, 2000
Summary
Coastal internal waves significantly impact low-frequency acoustic signals. This study correlated acoustic fluctuations with observed ocean processes, revealing internal waves
Area of Science:
- Oceanography
- Acoustics
- Geophysics
Background:
- Coastal internal waves are known to affect acoustic propagation.
- Previous studies lacked comprehensive environmental data for detailed correlation.
- Understanding these effects is crucial for sonar and underwater communication systems.
Purpose of the Study:
- To investigate the impact of coastal internal waves on low-frequency acoustic signals (50-500 Hz).
- To correlate acoustic fluctuations with specific oceanographic and geological processes.
- To analyze the effects of nonlinear internal waves on acoustic modal energy and travel time.
Main Methods:
- Conducted a large-scale, multidisciplinary experiment in the Mid-Atlantic Bight.
- Deployed a 16-element vertical line array (WHOI WVLA) in 70m water depth.
- Utilized tomography sources (224 Hz, 400 Hz) to establish an acoustic path anti-parallel to internal wave propagation.
Main Results:
- Observed strong semidiurnal effects on acoustic signals linked to internal wave solitons.
- Documented significant coupling of energy between acoustic modes due to internal waves.
- Found broadband fluctuations in modal intensity, travel-time, and temporal coherence.
- Noted sensitivity of acoustic pulse spread to solitons near the receiver.
Conclusions:
- Coastal internal waves are a primary driver of acoustic fluctuations in the studied region.
- Comprehensive environmental data is essential for understanding acoustic variability.
- Internal wave solitons near the receiver significantly influence acoustic pulse characteristics.
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