Underwater noise from submarine turbidity currents.

Area of Science:

• Geophysics
• Acoustics
• Sedimentology

Background:

• Turbidity currents are crucial for sediment transport in marine environments.
• Understanding the acoustic signatures of these currents can provide insights into their dynamics.
• Previous research has explored turbidity current flow but with limited acoustic data.

Purpose of the Study:

• To measure and analyze underwater acoustic noise generated by turbidity currents.
• To correlate noise spectra with particle size and flow characteristics.
• To investigate the sound generation mechanisms within these high-energy flows.

Main Methods:

• Underwater acoustic measurements were conducted in a fjord delta.
• Noise was recorded across a wide frequency range (1–1200 kHz).
• Analysis focused on noise spectra in relation to flow speed and particle composition.

Main Results:

• Acoustic spectra indicate sound generation primarily from collisions of sand-sized particles.
• Higher frequencies detected in the leading head suggest collisions involving finer particles.
• Noise intensity increased significantly (100-fold) with a moderate increase in flow speed (2-fold).

Conclusions:

• Particle collisions are a significant source of acoustic noise in turbidity currents.
• Differences in noise spectra between the head and body reflect variations in particle size.
• The findings support theoretical models of granular material collisions in turbulent flows.