Three-dimensional bottom diffraction in the North Pacific.

Area of Science:

• Ocean acoustics
• Acoustic propagation
• Seafloor interaction

Background:

• Bottom-interaction significantly influences deep water acoustic propagation.
• Bottom-diffracted surface-reflected (BDSR) paths involve energy scattering from discrete seafloor locations.
• BDSR paths were initially identified during the North Pacific Acoustic Laboratory experiment (NPAL04).

Purpose of the Study:

• To investigate bottom-diffracted surface-reflected (BDSR) paths in deep water acoustics.
• To analyze BDSRs in detail at the NPAL04 experimental site.
• To confirm the consistency of diffractor locations across different experiments and frequencies.

Main Methods:

• Analyzing acoustic propagation data from deep water experiments (NPAL04 and OBSANP).
• Identifying BDSR arrivals by examining pulse arrival times as a function of receiver range.
• Comparing diffractor locations identified in experiments with varying geometries and acoustic frequencies.

Main Results:

• BDSR paths were confirmed as dominant arrivals in quiet deep seafloor conditions.
• Diffraction points were identified on both featureless deep seafloor and seamount sides.
• Consistent diffractor locations were observed between NPAL04 and OBSANP experiments despite different geometries.
• The same location generated BDSRs for 77.5, 155, and 310 Hz transmissions during the OBSANP experiment.

Conclusions:

• BDSR paths are a significant and repeatable phenomenon in deep water acoustic propagation.
• Seafloor topography, including seamounts, plays a crucial role in acoustic energy scattering.
• The study validates the consistent identification of seafloor diffractors using acoustic methods across different experimental setups.