BUBBLE CLOUD EFFECT ON LOW- TO MID-FREQUENCY SOUND PROPAGATION IN MOBILE BAY, AL
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Authors
Bullard, Jeremy
Subjects
acoustic propagation
acoustics
Mobile Bay
estuarine front
bubble
soundscape
acoustics
Mobile Bay
estuarine front
bubble
soundscape
Advisors
Reeder, Davis B.
Date of Issue
2023-06
Date
Publisher
Monterey, CA; Naval Postgraduate School
Language
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, and 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 ~4 dB. During periods of frontal passage, decreases of ~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 ~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.
Type
Thesis
Description
Series/Report No
Department
Oceanography (OC)
Organization
Identifiers
NPS Report Number
Sponsors
Office of Naval Research (Code 32) One Liberty Center, 875 N. Randolph Street, Suite 4125, Arlington, VA 22203
Funding
Format
Citation
Distribution Statement
Approved for public release. Distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.