Monitoring of Global Acoustic Transmissions: Signal Processing and Preliminary Data Analysis

A great deal of controversy exists concerning the possible global warming trend which may occur as a result of a documented increase in atmospheric greenhouse gasses. The 1991 Heard Island Feasibility Experiment tested the feasibility of using transmissions of acoustic energy through major ocean bas...

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Bibliographic Details
Main Author: Frogner, Gary R.
Other Authors: NAVAL POSTGRADUATE SCHOOL MONTEREY CA
Format: Text
Language:English
Published: 1991
Subjects:
Physical and Dynamic Oceanography
Acoustics
*GREENHOUSE EFFECT
COMPUTER PROGRAMS
SIGNAL PROCESSING
FREQUENCY
DATA PROCESSING
PEAK VALUES
TEMPERATURE
GLOBAL
MONITORING
REAL TIME
RESOLUTION
THESES
TIME
CODING
FEASIBILITY STUDIES
SIGNALS
HEATING
SOUND TRANSMISSION
ACOUSTIC CHANNELS
DEEP DEPTH
DOPPLER EFFECT
PATTERNS
HYDROPHONES
RECEPTION
ARRIVAL
TIME DOMAIN
SOUTH(DIRECTION)
UNDERWATER SOUND
ISLANDS
INDIAN OCEAN
OCEAN BASINS
*GLOBAL TRANSMISSIONS
*ACOUSTIC TRANSMISSIONS
*SIGNAL PROCESSING
ACOUSTIC TOMOGRAPHY
ACOUSTIC VELOCITY
Heard Island
Indian
Online Access:http://www.dtic.mil/docs/citations/ADA246572
http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA246572
Description
Summary:A great deal of controversy exists concerning the possible global warming trend which may occur as a result of a documented increase in atmospheric greenhouse gasses. The 1991 Heard Island Feasibility Experiment tested the feasibility of using transmissions of acoustic energy through major ocean basins of the world to monitor spatially averaged global temperature trends. This thesis documents the Naval Postgraduate School's reception of the phase encoded signal transmitted from the Southern Indian Ocean, development of real-time signal processing software, and preliminary data analysis. Data, received from a 32-channel vertical array suspended in the deep sound channel off the coast of Monterey, CA, was processed using real-time capable software. Data processing to reduce noise, determine SNR, and remove the m-sequence coding was found to be quite sensitive to Doppler frequency shifts. Although the SNR of the raw data was only about -27.5 dB for individual hydrophones, the transmitted signal was detected in both the frequency and time domains. However, the maximum processed signal peak in the time domain had an SNR of only +9 dB which is insufficient for use in a long term global temperature monitoring project. As it provides inadequate arrival time resolution.

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