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Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing
Published on: February 13, 2018
Observed limiting cases of horizontal field coherence and array performance in a time-varying internal wavefield
The Journal of the Acoustical Society of America
|December 3, 2008
Summary
High-frequency acoustic signals were measured to understand how internal waves affect sound propagation. Results show that stronger underwater sound-speed anomalies reduce signal coherence, impacting acoustic communication.
Area of Science:
- Oceanography
- Acoustics
- Signal Processing
Background:
- Underwater sound propagation is influenced by environmental factors like internal waves.
- Acoustic signal coherence is crucial for underwater communication and sensing.
Purpose of the Study:
- To measure horizontal coherence of acoustic signals in the presence of internal waves.
- To investigate the relationship between sound-speed anomalies and acoustic coherence length.
Main Methods:
- Utilized a moored source and horizontal/vertical line array for acoustic measurements.
- Analyzed high signal-to-noise ratio (>=20 dB) signals from 100-1600 Hz.
- Compared measured horizontal field properties with modal decomposition of vertical signals.
Main Results:
- Horizontal coherence scales for 100 Hz signals ranged from 5 to 20 acoustic wavelengths.
- Coherence length was inversely related to the strength of episodic sound-speed anomalies caused by internal waves.
- Azimuthal field coherence properties were studied, separated from normal-mode interference.
Conclusions:
- Internal waves significantly impact horizontal acoustic coherence.
- Understanding these effects is vital for designing robust underwater acoustic systems.
- The study provides insights into acoustic field properties influenced by dynamic oceanographic conditions.
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