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A Review of Recent Developments in Underwater
A Review of Recent Developments in Underwater Acoustic Modeling
Acoustic ModelingUnderwater Acoustic Modeling
Acoustical Society of America Seattle WA • 23 27 May 2011
Acoustical Society of America Seattle, WA • 23-27 May 2011Seattle, WA • 26 May 2011
Paul C EtterPaul C. EtterPaper: 4pUW6
INTRODUCTION
• Objectives– Review developments in underwater acoustic modeling over the past eight years
Characterize evolution of the modeling inventory over 32 year period 1979 2011– Characterize evolution of the modeling inventory over 32-year period 1979 - 2011• Surveys conducted at eight-year intervals: 1979, 1987, 1995, 2003, 2011• 2003 survey published in book – provides baseline for 2011 survey
• Review modeling applicationsReview modeling applications– Domains of applicability– Emerging trends
• Identify Modeling Capabilities and Existing Inventoriesy g p g– Basic Acoustic Models
• Propagation Models• Noise Models• Reverberation ModelsReverberation Models
– Sonar Performance Models• Active Sonar Models• Model Operating Systems• Tactical Decision Aids
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• Tactical Decision Aids
• Provide model-selection guidance
MODELING APPLICATIONSDomains of Applicability
• Domains of Applicability– Arise from assumptions imposed while generating tractable mathematicalArise from assumptions imposed while generating tractable mathematical
solutions from governing physics or empirical data– Restrict applicability of models to specific frequency ranges or problem
geometries– May trade accuracy and computational complexity– Influenced by research versus operational applications
• ResearchC d t d i l b t i t– Conducted in laboratory environments
– Computer time is not a critical factor– Accuracy is important
• Operational• Operational– Conducted in the field– Require rapid execution, often under demanding conditions– Modeling accuracy may be subordinate to processing speedModeling accuracy may be subordinate to processing speed
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MODELING APPLICATIONSEmerging Trends
• Inverse Methods– geoacoustic and seismo-acoustic inversion– time-reversal acoustics
through the sensor parameter estimation– through-the-sensor parameter estimation– acoustic rain gauges
• Signal Processing– adjoint methods– stochastic resonancestochastic resonance– pulse propagation– clutter environments– vectors and clusters– prediction uncertainty in complex environments– high-frequency acoustics– high frequency acoustics– chaotic and stochastic nonlinear ray dynamics
• Underwater Acoustic Networks– channel models– advances in localization methods (range-based versus range-free schemes)advances in localization methods (range based versus range free schemes)– developments in rapid environmental assessments and new applications for gliders
• Marine-Mammal Endangerment– regulatory initiatives and environmental impacts– rising levels of underwater noise
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g– role of acidification: H2CO3 (carbonic acid) lowers pH, which lowers acoustic attenuation
– seismic operations and protection of whales
MODELING CAPABILITIES Model Hierarchy
• Underwater acoustics– Development and employment of
acoustical methods toI d t f t• Image underwater features
• Communicate information via the oceanic waveguide
• Measure oceanic properties
Modeling• Modeling– Method for organizing knowledge
accumulated through observation or deduced from underlying principles
– Physical (physics-based) models• Conceptual representation of
the physical processes occurring in the ocean
• Same as analytical modelsMathematical models– Mathematical models
• Empirical models– Based on observations
• Numerical models– Based on mathematical
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– Based on mathematical representations of the governing physics
MODELING CAPABILITIESPropagation Theory
2
2
22 1
tc ∂Φ∂
=Φ∇ tie ωφ −=Φ
• Frequency-Domain Solutions– Ray theory
022 =+∇ φφ k
( ) ( )zyxiGezyxF ,,,,=φ
k = ω / c
– Normal mode
– Multipath expansion
– Fast field / wavenumber integration
P b li i
( ) ( )rGzF ⋅=φ
( ) ( )θφ– Parabolic equation
• Environmental Range Dependence– Range independent (1D)
( ) ( )rGzrF ⋅= ,,θφ
0
Acoustically Acoustically
0
Acoustically AcousticallyAcoustically AcousticallyRange independent (1D)
f(z)
– Range dependent (2D, 3D)
f(z,r), f(z,r,θ) -200
-150
-100
-50
Wat
er D
epth
(m) Acoustically
ShallowAcoustically
Deep
Hypsometrically Shallow
Hypsometrically Deep-200
-150
-100
-50
Wat
er D
epth
(m) Acoustically
ShallowAcoustically
Deep
Hypsometrically Shallow
Hypsometrically Deep
Acoustically Shallow
Acoustically Deep
Hypsometrically Shallow
Hypsometrically Deep
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-25010 100 1000 10000 100000
Frequency (Hz)
yp y p-250
10 100 1000 10000 100000
Frequency (Hz)
yp y pyp y p
MODELING CAPABILITIESPropagation Models
Technique CAPARAY PLRAY ACCURAY GRAB LYBIN MPP RAYWAVE FACT RANGER BELLHOP GRASS LYCH Pedersen RP-70FLIRT C h t DELTA HARORAY MEDUSA Pl R SHALFACT
Range Independent Range Dependent
R Th FLIRT Coherent DELTA HARORAY MEDUSA PlaneRay SHALFACT GAMARAY FACTEX HARPO MIMIC PWRC TRIMAIN ICERAY FeyRay HARVEST MPC RAYSON XRAY AP-2/5 MODELAB ORCA ADIAB CPMS NAUTILUS WEDGE BDRM NEMESIS POPP ASERT FELMODE PROLOS WKBZ COMODE NLNM PROTEUS ASTRAL Kanabis PROSIM WRAP DODGE NORMOD3 SHEAR2 CENTRO KRAKEN SHAZAM 3D Ocean
Ray Theory
Normal Mode
FNMSS NORM2L Stickler CMM3D MOATL SNAP / C-SNAP COUPLE MOCTESUMA SWAMP
FAME NEPBR Integrated Mode MULE RAYMODE FFP OASES SAFARI CORE RD-OASES SAFRAN Kutschale FFP Pulse FFP SCOOTER OASES-3D RDOASP
Fast Field or Wavenumber
Integration
Multipath Expansion
MSPFFP RPRESS SPARC RDFFP RDOAST AMPE / CMPE HAPE OS2IFD RMPE 3DTDPACCUB / SPLN / CNP1 HYPER OWWE SNUPE 3DWAPE Corrected PE IFD Wide Angle PAREQ Spectral PE DREP IMP3D PDPE TDPE FDHB3D LOGPE PECan Two-Way PEFEPE MaCh1 PE-FFRAME ULETA
Use Single Environmental Specification
Integration
Parabolic Equation
FEPE MaCh1 PE FFRAME ULETA FEPE-CM MONM3D PESOGEN UNIMOD FEPES MOREPE PE-SSF (UMPE / MMPE) 3DPE (NRL-1) FOR3D NSPE RAM / RAMS / RAMGEO 3DPE (NRL-2)
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Baseline Reference: P.C. Etter, Underwater Acoustic Modeling and Simulation (Taylor & Francis, 2003, 3rd edition).
New since 2003 baseline
MODELING CAPABILITIESSelection Guidance for Propagation Models
Model type
ApplicationsShallow water Deep water
Low frequency High frequency Low frequency High frequencyRI RD RI RD RI RD RI RD
Ray theory
Normal mode
Multipath expansion
Fast field
Parabolic equation
[Originally adapted from Jensen (1982)]
Low frequency (< 500 Hz) RI: Range-independent environment
High frequency (> 500 Hz) RD: Range-dependent environment
Modeling approach is both applicable (physically) and practical (computationally)
[Originally adapted from Jensen (1982)]
Modeling approach is both applicable (physically) and practical (computationally)
Limitations in accuracy or in speed of execution
Neither applicable or practical
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. . . Updated Domains of Applicability
MODELING CAPABILITIESNoise Theory
8090
100110• Ambient Noise
– DeterministicSea State: 3
Shipping Level: 5
1020304050607080
dB
Deterministic
– Level
– Directionality
Shipping noise
Shipping Level: 5
010
1 10 100 1000 10000 100000
Frequency (Hz)
– Shipping noise
– Weather noise
• Beam-Noise Statistics• Beam Noise Statistics– Stochastic
• Analytic
Sim lation
ijkijkijk
A
k
n
j
m
iBZS
ij
∑∑∑=== 111• Simulation
– Large-aperture beam noise
– Shipping noise
kji === 111
m = number of routes in the basinn = number of ship typesAij = number of ships of type j on route i
[Adapted from Moll et al. (1979)]
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Aij number of ships of type j on route iSijk = source intensity of the kth ship of type j on route iZijk = intensity transmission ratio from ship ijk to receiving pointBijk = gain for a plane wave arriving at the array from ship ijk
MODELING CAPABILITIESNoise Models
Ambient Noise Beam-Noise Statistics ANDES AMBENT BBN Shipping Noise ARAMIS BTL CANARY USI Array Noise
Analytic
CNOISE Sonobuoy Noise DANES DANM DINAMO BEAMPL
S S
Simulation
DUNES DSBN FANM NABTAM ISAAC SIAM - I / II Normal Mode Ambient NoiseRANDI I / II / III RANDI - I / II / III
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Baseline Reference: P.C. Etter, Underwater Acoustic Modeling and Simulation (Taylor & Francis, 2003, 3rd edition).
New since 2003 baseline
MODELING CAPABILITIESReverberation Theory
• Formulations– Cell scattering
Ocean divided into cells• Ocean divided into cells
• Uniformly distributed scatterers
• Sum contributions of all cells
– Point scattering
TargetBistatic
g
• Statistical distribution of scatterers
• Sum echoes from each scatterer
• Source-Receiver Geometry
[Originally adapted from Hodgkiss (1984)]
Source
Bistatic• Source Receiver Geometry– Monostatic - collocated
– Bistatic - separated in range / depth
– Multistatic – multiple sources / receiversp
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Receiver
MODELING CAPABILITIESReverberation Models
Cell Scattering Point ScatteringMonostatic Bistatic Monostatic Bistatic
C-SNAP-REV ARTEMIS REVGEN BORIS-SSA DOP BAM RITSHPA Under-Ice Reverberation EIGEN / REVERB BiKR SimulationHYREV BiRASP
Cell Scattering Point Scattering
HYREV BiRASP MAM BISAPP PAREQ-REV BISSM PEREV BISTAR PERM-2D OGOPOGO REVMOD RASP REVPA RUMBLE REVSIM S-SCARAB R-SNAP TENAR
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Baseline Reference: P.C. Etter, Underwater Acoustic Modeling and Simulation (Taylor & Francis, 2003, 3rd edition).
New since 2003 baseline
MODELING CAPABILITIESSonar Performance Theory
• Active Sonar Performance– Stand-alone models
SL = Source Level (of sonar)TL = Transmission Loss (one way)TS = Target StrengthNL = Noise LevelStand alone models
– Solve active sonar equations
RDDINLTSTLSL 2 RDRLTSTLSL 2
DI = Directivity IndexRL = Reverberation LevelRDN = Recognition Differential (noise-limited)RDR = Recognition Differential (reverberation-limited)
• Model Operating Systems
NRDDINLTSTLSL +−=+− 2 RRDRLTSTLSL +=+− 2
– System architectures (executive/bundled)
– Multiple component models
– Data-management software
• Tactical Decision Aids– Operational guidance and training
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– Visualization techniques
MODELING CAPABILITIESSonar Performance Models
Active RAYMODE MOCASSINALMOST MOC3D
Active Sonar Models
ALMOST MOC3D ASPM MODRAY CASTAR MSASM CONGRATS NISSM - II ESPRESSO SEARAY GASS SONAR HODGSON SST INSIGHT SUPREMO INSTANT SWAMI / DMOSLIRA SWAT LIRA SWAT LORA UAIM MINERAY
CAAM HydroCAM ASPECTModel Operating Systems Tactical Decision Aids
CALYPSO PRISM IMAT CASS SPPS NECTA GSM - Bistatic
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Baseline Reference: P.C. Etter, Underwater Acoustic Modeling and Simulation (Taylor & Francis, 2003, 3rd edition).
New since 2003 baseline
SUMMARY
• Characterized modeling applications in terms of:– Domains of applicability– Emerging trends
• Identified available models– Current inventory comprises:
Emerging trends
• 128 propagation models• 21 noise models• 28 reverberation models• 35 sonar-performance models
Inventory updated at 8 year intervals:– Inventory updated at 8-year intervals: 1979, 1987, 1995, 2003, 2011
– Approximately 5 models have been added to the inventory each year
zero-intercept ~ 1967
• Provided model selection guidance for research and operational applications
Ob ti M d l t b i di t f R&D i t t
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• Observation – Models appear to be proxy indicators of R&D investments.