Angle estimation of single and overlapping echoes with a broadband split-beam echosounder

Area of Science:

• Acoustical oceanography
• Marine bioacoustics
• Signal processing

Background:

• Split-beam echosounders are vital for marine organism abundance and behavior studies.
• Accurate angle of arrival (AoA) estimation is critical for target strength and spatial positioning.
• Existing AoA methods (split-aperture correlator) are outdated for broadband systems.

Purpose of the Study:

• To assess the split-aperture correlator's (SAC) accuracy for broadband split-beam echosounders.
• To develop and evaluate novel methods for broadband AoA estimation.
• To improve the characterization of marine organisms using advanced acoustic techniques.

Main Methods:

• Assessed the split-aperture correlator (SAC) for broadband systems.
• Developed an extended SAC to address limitations with frequency-dependent targets.
• Introduced a broadband maximum likelihood estimator for overlapping echoes and spectra.

Main Results:

• Demonstrated SAC's inaccuracy for broadband single echoes from targets like gas-bearing fish.
• The extended SAC showed improved performance for specific broadband targets.
• The maximum likelihood estimator accurately estimated AoAs and spectra of overlapping echoes in laboratory settings.

Conclusions:

• The traditional SAC method is inadequate for modern broadband split-beam echosounders.
• New broadband estimation techniques are necessary for accurate marine acoustic studies.
• The developed maximum likelihood estimator offers a promising solution for complex acoustic environments.