Mid-frequency acoustic tracking of breaking waves

Area of Science:

• Oceanography
• Acoustics
• Wave dynamics

Background:

• Surface wave breaking is a significant source of oceanic noise.
• A mid-frequency planar array (130m depth, 1m aperture) can detect these events acoustically at 5-6 kHz.
• Beamforming alone has limitations in accurately tracking sources due to array geometry.

Purpose of the Study:

• To develop and validate a method for accurately tracking the trajectories of large surface wave breaking events.
• To overcome the limitations of traditional beamforming for source localization in this context.

Main Methods:

• Splitting the planar array into sub-arrays.
• Beamforming each sub-array toward the acoustic source.
• Computing temporal cross-correlations of sub-array beams to estimate source location.

Main Results:

• Successfully estimated source tracks of wave breaking events.
• The estimated trajectories closely matched those observed in aerial imagery.
• The cross-correlation method enhanced tracking accuracy compared to beamforming alone.

Conclusions:

• Acoustic tracking of surface wave breaking is feasible using sub-array cross-correlation techniques.
• This method provides accurate trajectory estimation, complementing visual observations.
• The findings have implications for acoustic monitoring of ocean surface processes.