Simulation of acoustic multipath arrival structure in the Barents Sea.

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by  Elliott, John M.;Chiu, Ching-Sang.;Miller, James H.

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6c.ADDRESS(City,State,andZIPCode) 7b.ADDRESS(Cry,State,andZIPCode)
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11.TITLE(IncludeSecurityClassification)
SIMULATIONOFACOUSTICMULTIPATHARRIVALSTRUCTUREINTHEBARENTSSEA
12.PERSONALAUTHOR(S) Elliott,JohnM.
13a.TYPEOFREPORT 13b.TIMECOVERED 14.DATEOFREPORT(year,month,day) 15.PAGECOUNT
Master'sThesis From To 1992,June 110
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TheviewsexpressedinthisthesisarethoseoftheauthoranddonotreflecttheofficialpolicyorpositionoftheDepartmentofDefenseortheU.S.
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17.COSATICODES 18.SUBJECTTERMS(continueonreverseifnecessaryandidentifybyblocknumber)
FIELD GROUP SUBGROUP AcousticTomography,OceanAcoustics,Oceanography,BarentsSea
19.ABSTRACT(continueonreverseifnecessaryandidentifybyNocknumber)
InsupportoftheBarentsSeaPolarFrontExperiment(BSPPEX)inSeptember1992(BarentsSeaPolarFrontGroup, 1992),theplanned224Hz
tomographysignaltransmissionsfromanearbottomsoundsourcetoaverticalreceiverarrayconsistingof16hydrophonesweresimulated.
Acousticraysweretracedtothereceiverarrayatarangeof50kmusingtheNOAAHamiltonianRaytracingProgramfortheOcean(HARPO).
InputtoHARPOwasamathematicaloceanenvironmentbasedonhistoricalbathymetricandsoundspeeddata. Acousticmultipatharrival
structurewasconstructedthrougheigenraysearchesandestimationofraytubespreadingandsurfaceandbottomlosses. Aresolvabilityanalysis
ofthesimulatedarrivalstructurerevealsthatthereareatotalof49uniqueresolvablerayarrivals. Amongthem,42arefromindividual
omnidirectionalhydrophonesand7fromplanewavebeamforming.
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Dr.Ching-SangChiu 408-646-3239 OC/Ci
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SIMULATION OF ACOUSTIC MULTIPATH
ARRIVAL STRUCTURE IN THE BARENTS SEA
by
John M. Elliott
LieutenantCommander, United StatesNavy
B.S., UniversityofFlorida, 1977
M.E., University ofFlorida, 1978
Submitted in partial fulfillment
ofthe requirementsforthe degreesof
MASTER OF SCIENCE IN PHYSICAL OCEANOGRAPHY
MASTER OF SCIENCE IN ENGINEERINGACOUSTICS
from the
ABSTRACT
In support of the Barents Sea Polar Front Experiment (BSPFEX)
in September 1992 (Barents Sea Polar Front Group, 1992), the
planned 224 Hz tomography signal transmissions from a near bottom
sound source to a vertical receiver array consisting of 16
hydrophones were simulated. Acoustic rays were traced to the
receiver array at a range of 50 km using the NOAA Hamiltonian
Raytracing Program for the Ocean (HARPO). Input to HARPO was a
mathematical ocean environment based on historical bathymetric and
sound speed data. Acoustic multipath arrival structure was
constructed through eigenray searches and estimation of raytube
spreading and surface and bottom losses. A resolvability analysis
of the simulated arrival structure reveals that there are a total
of 49 unique resolvable ray arrivals. Among them, 42 are from
individual omnidirectional hydrophones and 7 from plane wave
beamforming.
in
3(s>7
TABLE OF CONTENTS
...................
I. INTRODUCTION 1
...........
A. OCEAN ACOUSTIC TOMOGRAPHY 1
B. BARENTS SEA POLAR FRONT EXPERIMENT 2
C. THESIS OBJECTIVES AND APPROACHES 6
D. THESIS OUTLINE 7
. .
II. PHYSICAL OCEANOGRAPHY 9
A. INTRODUCTION 9
.
B. WATER MASSES AND SURFACE WAVES 9
.
C. BARENTS SEA POLAR FRONT 12
III. ACOUSTIC EFFECTS 15
A. INTRODUCTION 15
.
B. ABSORPTION 15
C. SPREADING AND REFRACTIVE EFFECTS 15
.
D. SURFACE LOSS 16
E. BOTTOM LOSS 18
IV. RAY THEORY ACOUSTICS 20
A. INTRODUCTION 20
B. HAMILTONIAN RAY TRACING 20
C. HARPO OVERVIEW 21
IV
D. MODELING THE BARENTS SEA ACOUSTIC ENVIRONMENT 22
.
1. General 22
2. Sound Speed Field, Bathymetry, and Sea
Surface 23
3. Summary 27
V. ARRIVAL STRUCTURE SIMULATION & ANALYSIS 29
A. INTRODUCTION 29
B. RAY PATH STRUCTURE 29
C. ARRIVAL STRUCTURE 30
D. ARRIVAL TIME STRUCTURE 32
E. RELATIVE AMPLITUDE 34
F. RESOLVABILITY ANALYSIS 39
1. Introduction 39
2. Method I - Individual Hydrophones 40
a. Time Analysis 40
b. a Analysis 41
t
c. Resolvable Rays 43
3. Method II - Plane Wave Beamformer 46
VI. CONCLUSIONS 51
'
LIST OF REFERENCES 53
APPENDIX A: LIST OF EXTERNAL PROGRAMS 55
APPENDIX B: INDIVIDUAL HYDROPHONE RESOLVABILITY
ANALYSIS TABLE 81
.
APPENDIX C: LINE ARRAY RESOLVABILITY ANALYSIS TABLE 92
. .
INITIAL DISTRIBUTION LIST 98
VI