Ambient noise forecasting with a large acoustic array in a complex shallow water environment.

Area of Science:

• Oceanography
• Acoustics
• Signal Processing

Background:

• Ocean ambient noise forecasting is crucial for sonar system performance characterization.
• Accurate noise prediction enhances operational capabilities and future performance projections.
• Existing methods can be improved with precise source localization and bearing resolution.

Purpose of the Study:

• To enhance ocean ambient noise forecasting using a priori source position knowledge.
• To validate the effectiveness of a novel forecasting approach with real-world data.
• To quantify the accuracy of the proposed noise forecasting method.

Main Methods:

• Utilized radar and Automatic Identification System (AIS) for source positioning.
• Computed transmission loss (TL) from known source positions to a large aperture research array.
• Estimated individual ship source levels (SLs) using non-negative least squares and array beam response.
• Generated ambient noise forecasts by projecting estimated SLs along ship tracks.

Main Results:

• Successfully estimated individual ship source levels (SLs).
• Developed a method for projecting estimated SLs along known ship tracks to form noise forecasts.
• Achieved a mean-squared error as low as 3.5 dB in 30-minute ambient noise forecast estimates.
• Demonstrated the effectiveness of integrating source position data into noise forecasting.

Conclusions:

• The integration of precise source positions and bearing resolution significantly improves ocean ambient noise forecasting.
• The developed method provides accurate short-term (30-minute) ambient noise predictions.
• This approach offers a valuable tool for characterizing and projecting sonar system performance in dynamic ocean environments.