Mid to High Frequency (1-20 kHz) Acoustics at the Central Area, August 9-20
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Transcript of Mid to High Frequency (1-20 kHz) Acoustics at the Central Area, August 9-20
Mid to High Frequency (1-20 kHz) Acoustics at the
Central Area, August 9-20
Science measurement goal: measure contemporaneously MF acoustics and influencing environmental scales for ocean acoustic modeling and interpretation
Applied Physics LaboratoryUniversity of Washington
Peter H. Dahl, Jee Woong Choi
Acoustic Measurements: •Bottom Loss (20log|R|) 1-20 kHz, Grazing Angles 10-80o
•3D Spatial Coherence (single and multi-paths)•Sea Surface (energy) Loss (single and multi-paths)
•Sea Surface backscattering (11-60 kHz)Environmental Measurements:
•Directional Wave •MORAY 1+ acoustic receiving array aux data: air & sea temp and sea surface elevation
-0.5 0 0.5 1 1.5 2 2.5-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
X (km)
Y (
km)
APL LEAR DeploymentsSMALLER SCALE VIEW
500 m
U-Miamiwave buoy
WHOI environmental mooring
APL-UW wave buoy
MORAY 1+ VLA/HLA ReceivingArray
Ship-deployed source location(via precise positioning of R/V Knorr)
Track of the R/V Endeavorfor internal wave & acousticpropagation study
3 1 5 9 13M1+
4
8
12
16
B1
B2
50 m
500 m
100 m
200 m
300 m
1000 m KEM 1000
500 m1000 m
71115A1A2
2
6
10
14
Shark
500 m
U Miami
1000 m
300o
Basic Layout for MF measurements aboutthe MORAY 1+ VLA/HLA system
X
YX Y : size of 1st Fresnel zone (m)
A B C D E F G H
Grazingangle 54 62 35 43 19 25 13 17
1 kHz 6 9 5 9 17 12 13 12 47 17 35 17 86 21 64 21
20 kHz 1 2 1 2 4 3 3 3 11 4 8 4 20 5 15 5
BOTTOM REFLECTION0m 50m 100m 200m 300m
A B C D E F G H
80m40m
25m
50m
C5 position (200 m range)
0 20 40 60 80 10 120 140 160 180 200
0
10
20
30
40
50
60
70
RANGE (m)
SD: 40 m RD: 25 m
RANGE (m)
SD: 40 m RD: 50 m0
10
20
30
40
50
60
70
0 20 40 60 80 10 120 140 160 180 200
100 150 200 250-0.4
0.4
TIME (ms)
MF output(8-16 kHz)
100 150 200 250-0.4
0.4
TIME (ms)
MF output(8-16 kHz)
0
10
20
30
40
50
60
70
800 50 100 150 200 250
RANGE (m)
SD: 40 m RD: 25 m
300
0
10
20
30
40
50
60
70
800 50 100 150 200 250
RANGE (m)
SD: 40 m RD: 50 m
300
C13 position (300 m range)
180 200 220 240 260 280 300 320-0.5
0.5
TIME (ms)
180 200 220 240 260 280 300 320-0.5
0.5
TIME (ms)
3 1 5 9 13M1+
4
8
12
16
71115
2
6
10
14300o
start
C1 C13 direction
-5
0
5
10
15
201 kHz
BO
TT
OM
LO
SS
10 30 50 7020 40 60
20 40 60-5
0
5
10
15
20
BO
TT
OM
LO
SS
3 kHz
10 30 50 70
20 40 60-5
0
5
10
15
20
GRAZING ANGLE (deg.)
BO
TT
OM
LO
SS 6 kHz
10 30 50 70
20 40 60-5
0
5
10
15
2010 kHz
10 30 50 70
20 40 60-5
0
5
10
15
2014 kHz
10 30 50 70
20 40 60-5
0
5
10
15
2020 kHz
GRAZING ANGLE (deg.)10 30 50 70
3 1 5 9 13M1+
4
8
12
16
71115
2
6
10
14300o
start
C1 C13 direction
C2 C14 direction
-5
0
5
10
15
201 kHz
BO
TT
OM
LO
SS
10 30 50 7020 40 60
20 40 60-5
0
5
10
15
20
BO
TT
OM
LO
SS
3 kHz
10 30 50 70
20 40 60-5
0
5
10
15
20
GRAZING ANGLE (deg.)
BO
TT
OM
LO
SS 6 kHz
10 30 50 70
20 40 60-5
0
5
10
15
2010 kHz
10 30 50 70
20 40 60-5
0
5
10
15
2014 kHz
10 30 50 70
20 40 60-5
0
5
10
15
2020 kHz
GRAZING ANGLE (deg.)10 30 50 70
C1 C13 C2 C14
C3 C15 C4 C16
Knorr move out at 0.1 m/s Continuous Angle Study Range: 50-300 m
50 m
250 mTime (ms)
80 m80.2 m
81 m
84.9 m
95 m
Water~1485 m/s
1600 m/s
1720 m/s
1560 m/s
1750 m/s
Half space1900 m/s
Geoacoustic model
for the site
PE-derived bottom loss (Seattle 06 meeting)
M1-M13 direction M2-M14 direction
10 20 30 40 50 60 70-5
0
5
10
15
20
GRAZING ANGLE (deg.)
BO
TT
OM
LO
SS
(dB
) 2 kHz
10 20 30 40 50 60 70-5
0
5
10
15
20
GRAZING ANGLE (deg.)
BO
TT
OM
LO
SS
(dB
) 4 kHz
Studies on Sea Surface Boundary Effects
LF (swell) from the South
HF (wind waves) from the East
Wave Conditions 10 August
3 1 5 9 13M1+
4
8
12
16
B1
B2
50 m
500 m
100 m
200 m
300 m
1000 m KEM 1000
500 m1000 m
71115A1A2
2
6
10
14
Shark
500 m
U Miami
1000 m
300o
DIFFERENT PROPAGATIONDIRECTIONS THROUGH THE DIRECTIONAL WAVE FIELD
kD/2
Coh
eren
ce M
agni
tude
Knock Down of Horizontal Spatial Coherence at High Sea State
0 2 4 6 8 10 120
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2 4 6 8 10 120.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
kD/2
Horizontal Coherence Vertical Coherence
15 AUG 12m/s
9 AUG 4m/s
2 4 6 8 10 12 14 16 18 20-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
Frequency (kHz)
Energy loss due to near surface bubbles for single surfaceinteraction at grazing angle 15o
(Preliminary results—heavy averaging)Very interesting applied and basic implications….
Lo
ss (
dB
)
< 10 kHz, ~0 dB
> 10 kHz, ~3 dB
The road ahead
Key data needs:
ASIS buoy and wind speed (to replace Knorr IMET) [Graber & Williams]
bottom strategraphy, layering and roughness+ cores in the central area [Tang, Goff, Turget, Wang]
Mooring CTD in the central area (from “forest mooring”) [Duda et al.]
Later on, surface modeling (to extend observations) [Plant’s model]
First (three) lines of inquiry:
-Towards one geoacoustic model for the Central Site consistent overLF-MF experimental groups
-3D spatial coherence: role of sea surface, (use of small slope approx.)kH >> 1 roughness
-Spatial coherence of bottom forward reflection and relation tokH<< 1 roughness