Green's function approximation from cross-correlation of active sources in the ocean

Area of Science:

• Oceanography
• Acoustics
• Geophysics

Background:

• Ocean acoustic interferometry uses ambient noise cross-correlation to estimate Green's functions.
• Passive noise sources have limitations in frequency, control, and monitoring continuity.

Purpose of the Study:

• To experimentally investigate active sources for ocean acoustic interferometry.
• To compare active source performance with passive noise cross-correlation.
• To analyze the accuracy of empirical Green's function estimates from active sources.

Main Methods:

• Experimental deployment of active acoustic sources in two configurations: vertical lowering and horizontal towing.
• Cross-correlation analysis of recorded acoustic data.
• Comparison of experimental results with theoretical predictions and simulations.

Main Results:

• Active sources provide higher frequencies and better control for ocean acoustic interferometry.
• Both vertical and horizontal active source configurations accurately approximate direct acoustic paths.
• Surface-reflected paths are more accurately estimated with greater hydrophone horizontal separation.

Conclusions:

• Active sources are a viable and advantageous alternative to passive noise for ocean acoustic interferometry.
• Source configuration impacts the accuracy of secondary path estimation.
• Further research can refine active source methods for enhanced underwater acoustic monitoring.