Bubble Cloud Effect on Low-to Mid-Frequency Sound Propagation in Mobile Bay, AL
Abstract
The Mobile Bay Estuary Acoustic Field Experiment 2021 (MBE2021) was funded by the Office of Naval Research (ONR) as part of the multi-university Undersea Remote Sensing (USRS) program directed by Dr. Reginald Beach (ONR 322). During the experiment, environmental and acoustic data were collected June 9-15, 2021, in the vicinity of the mouth of Mobile Bay, AL, focused on assessing the impact on acoustic propagation by tidal fronts. A linear frequency-modulated acoustic signal from 500-5000 Hz was transmitted throughout the tidal cycle. This signal was measured by multiple moored receivers to determine the energy that passed between the source and receiver before, during, and after frontal passage. Nominal variations due to changes of acoustic ray paths were approx. 4 dB. During periods of frontal passage, decreases of approx. 7 dB were observed over the scale of minutes. This increase in transmission loss is likely due to bubbles carried by the tidal front. ROMS model predictions indicate that a submerged sound channel exists for approx. 1 hour during the tidal ebb, creating a depth-dependent feature that supports extended propagation ranges. These physical factors indicate that the tidal front can create an exploitable submerged sound channel, while at the same time transmission through the front will experience additional loss beyond what is currently modeled.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2023
- Accession Number
- AD1213127
Entities
People
- Jeremy Bullard
Organizations
- Naval Postgraduate School