Mid-frequency geoacoustic inversion using bottom loss data from the Shallow Water 2006 Experiment

Area of Science:

• Ocean acoustics
• Geophysics
• Signal processing

Background:

• Traditional geoacoustic inversion focuses on low frequencies (<1 kHz) with simplified models.
• Navy sonar systems operate at mid-frequencies (1-10 kHz), necessitating inversion methods for this band.
• Limited research exists on mid-frequency geoacoustic inversion.

Purpose of the Study:

• To demonstrate the feasibility of geoacoustic inversion using mid-frequency (2-5 kHz) bottom loss data.
• To analyze the impact of seafloor topography on acoustic propagation at mid-frequencies.
• To compare inversion results with direct measurements and other techniques.

Main Methods:

• Utilized acoustic measurements from the Shallow Water 2006 Experiment.
• Employed a half-space geoacoustic model with three parameters (density, compressional wave speed, attenuation).
• Performed inversion by fitting the model to bottom loss data in a least-squares sense.

Main Results:

• Successfully demonstrated geoacoustic inversion at mid-frequencies (2-5 kHz).
• Inverted sediment sound speed and attenuation values were consistent with direct measurements.
• Forward scattering from topographical changes was identified as crucial at mid-frequencies.

Conclusions:

• Mid-frequency geoacoustic inversion is viable and provides valuable insights into seafloor properties.
• Seafloor topography significantly influences mid-frequency sound propagation and requires consideration in models.
• Averaging measurement techniques may be necessary to address fine-scale topographic variability in future studies.