Related Experiment Videos
Matched-field processing gain degradation caused by tidal flow over continental shelf bathymetry
Marshall H Orr1, Peter C Mignerey
1Acoustics Division, Naval Research Laboratory, Washington, DC 20375-5320, USA.
The Journal of the Acoustical Society of America
|June 27, 2002
Summary
Tidal flow significantly degrades matched-field processing gain in shallow waters by altering acoustic signal phase. Continuous updates of processor replica fields are needed to maintain signal processing gain in these dynamic environments.
Area of Science:
- Ocean Acoustics
- Signal Processing
- Environmental Fluid Dynamics
Background:
- Shallow water environments exhibit complex acoustic propagation due to variable bathymetry and tidally driven stratified flow.
- Matched-field processing (MFP) is sensitive to environmental changes, potentially leading to signal processing gain degradation.
Purpose of the Study:
- To quantify the variability of MFP gain degradation in shallow water channels.
- To investigate the impact of tidally driven flow and variable bathymetry on acoustic signal properties and MFP performance.
Main Methods:
- Measured temporally variable sound-speed profiles during ebb and slack tidal flows.
- Calculated acoustic signal phase changes over a 9.3 km range.
- Estimated MFP gain degradation for a full water column vertical array.
Main Results:
- A 3-9 dB degradation in coherent MFP output was observed, primarily caused by acoustic signal phase changes.
- Acoustic signal properties and MFP gain exhibit continuous, predictable changes over a tidal cycle.
- Repeatable changes in phase coherent properties of acoustic signals were noted across successive tidal cycles.
Conclusions:
- Tidally driven flow and variable bathymetry create dynamic shallow water acoustic channels.
- Regular updates of MFP replica fields are essential to maintain processor gain in shelf/slope environments.
- Understanding these predictable acoustic variations is crucial for effective underwater acoustic signal processing.