Modeling intensity fluctuations of
acoustic transmissions from the R/V
Sharp during SW06
Georges Dossot, James H. Miller, Gopu R. Potty, Dept. of Ocean Engineering, URI
James F. Lynch, Arthur E. Newhall, Ying Tsong Lin, WHOI
Mohsen Badiey, University of Delaware
Kevin Smith, D. Benjamin Reeder, Naval Postgraduate School
158th Acoustical Society of America meeting
San Antonio, Texas, October 2009
Outline
SW06 & R/V Sharp
• 50+ events
• Different locations
Specific internal wave events
• Event 44 (past work)
• Similar events (new work)
Modeling
• Simplified model
• Looking forward → Modeling real environment
SW06 Test Site & R/V Sharp Locations
SW06 Test Site & R/V Sharp Locations
5 km
39.25
R/V Sharp & SW06:
60
80
SW33
70
C3 (3)
70
70
39.15
60
SW29
B1B (5)
39.1
70
-73.35
-73.3
-73.25
-73.2
A1A (4)
80
SW31
SW30
SHARK
80
B5A (2)
39.05
C1A
(3)(4)
C1B
C1D (3)
B1 (9)
SW32 B1A (5)
C5A (4)
70
Latitude (degrees)
39.2
•180 hours of acoustic transmissions
• Various ranges and bearings
•50+ internal wave events witnessed
-73.15
-73.1
-73.05
-73
Longitude (degrees)
Acoustic Transmission Paths
SW06 Acoustic Sources
SHRUs
Ship Positions
Environmental Moorings
-72.95
-72.9
-72.85
Interested in sourceSW34
receiver path near
parallel to approaching
internal waves
M. Badiey, B. G. Katsnel’son, J. Lynch, S. Pereselkov, “Frequency dependence and intensity fluctuations due to shallow
water internal waves,” J. Acoust. Soc. Am. 122, 747-760 (2007)
Objectives
Research
Vessel
SHARK Array
Examine intensity fluctuations over time…
Propagating Internal
Wave
→ before, during, and after internal wave events
Examine intensity fluctuations over space…
→ depth and modal dependence
Statistically characterize intensity fluctuations…
I (( z || N ), k , t , f )
( z  Depth, or N  Mode Number)
k  Chirp arrival number t  Time f  Frequency
B. G. Katsnel’son, J. Lynch, A. V. Tshoidze, “Space-Frequency Distribution of Sound Field Intensity in the Vicinity of the Temperature
Front in Shallow Water,” Acoustical Physics 53(5), 611-617 (2007)
Intensity Measurements
Integrated Energy: I z (k )   dz  d I ( , z , k )
Temporally Integrated Energy: I ( z, k )   d I ( , z, k )
Point Observations of Broadband Intensity: I ( , z, k )
Observations of Point Scintillations:
SI 
I2
I
2
1
Point Observations of Peak Intensity: I P ( z, k )  max  [ I ( , z, k )]
Observations of Modal Amplitudes:
I (N , k, f )
A. Fredericks, J. A. Colosi, J. Lynch, C. Chiu, and P. Abbot, “Analysis of multipath scintillation from long range acoustic transmissions
on the New England continental slope and shelf,” J. Acoust. Soc. Am. 117, 1038–1057 (2005)
Duda, T.F., Lynch, J.F., Newhall, A.E., Lixin Wu, Ching-Sang Chiu, “Fluctuation of 400-Hz sound intensity in the 2001 ASIAEX South
China Sea experiment,” Oceanic Engineering, IEEE Journal of, 29(4), 1264 – 1279 (2004)
Outline
SW06 & R/V Sharp
• 50+ events
• Different locations
Specific events
• Event 44 (past work)
• Similar events (new work)
Modeling
• Simplified model
• Looking forward → Modeling real environment
Event 44 “Point” Observations
‘ramping’ before arrival of internal wave
Note warm water bottom intrusion
Event 44 depth dependance
Temporally Integrated Energy - Phone 1, z = 13.5 m
Phone 1 Distribution
I(z,k)
10
300
200
5
100
0
0
Temporally Integrated Energy - Phone 4, z = 24.75 m
Phone 4 Distribution
I(z,k)
10
300
200
5
100
0
0
Temporally Integrated Energy - Phone 10, z = 47.25 m
Phone 10 Distribution
I(z,k)
10
600
Depth dependant variability
400
5
200
0
0
I(z,k)
Temporally Integrated Energy - Phone 14, z = 77.25 m
Phone 14 Distribution
10
200
5
100
0
03:00
06:00
09:00
Time Transmitted
12:00
0
Event 46 (new)
Trapped sound between solitons?
Event 47 (new)
Notice quiet conditions both before
& after internal wave activity
Event 47 (new)
Slight ‘ramping’ before arrival of internal wave
Intensity "Point" Observations
10
Number of arrivals
I(,z,k)
8
6
4
2
0
Intensity "Point" Observations Distribution
1500
200 400 600 800
Transmission number
1000
500
0
0
2
4
I( ,z,k)
6
8
Event 47 (new)
Temporally Integrated Energy - Phone 1, z = 13.5 m

I (z,k)
15
Phone 1 Distribution
300
10
200
5
100
0
0
Temporally Integrated Energy - Phone 4, z = 24.75 m

I (z,k)
15
Phone 4 Distribution
300
10
200
5
100
0
0
Temporally Integrated Energy - Phone 10, z = 47.25 m

I (z,k)
15
Phone 10 Distribution
300
10
200
5
100
0
0
Temporally Integrated Energy - Phone 14, z = 77.25 m

I (z,k)
15
Phone 14 Distribution
300
10
200
5
100
0
21:00
22:00
23:00
Time Transmitted
00:00
0
Lack of warm water intrusion near bottom → less depth dependant variability
Outline
SW06 & R/V Sharp
• 50+ events
• Different locations
Specific events
• Event 44 (past work)
• Similar events (new work)
Modeling
• Simplified model
• Looking forward → Modeling real environment
Modeling
Using 3D PE model provided by NPS, start with a simple scenario
Assumptions:
50 m depth slice
4 km range slice
• 5km × 5km × 100m water
column
• Flat bottom
• Single layer soundspeed
properties for sediment
• Source at 75 m depth
• Single soliton marches
eastward
• Same source-receiver angle
as in Event 44
• Virtual VLA 4 km away from
source
TL (dB re 1m), soliton 2500 m away
0
50
20
60
40
50
4
60
3
70
2
80
90
1
90
100
0
70
60
TL (dB re 1m), soliton 2500 m away
5
80
80
Range (km)
depth (m) at 4km Range
Modeling
100
-2
0
2
Cross-Range (km)
-2
0
2
Cross-Range (km)
100
Modeling
I(,z,k)
2
1.5
1
0.5
0
Intensity "Point" Observations Distribution
100
Number of arrivals
Intensity "Point" Observations
2.5
5
10
15
Transmission number
80
60
40
20
0
0.5
1
1.5
I(,z,k)
2
2.5
Although not quite as dramatic, the same ramping trend is evident as soliton
moves closer. Modeled distribution similar to that of measured data.
Modeling: Next steps
→ Modeling inputs for bathymetry and sediment properties to be taken
from data and literature
G. R. Potty, J. H. Miller, P. S. Wilson, J. F. Lynch, A. Newhall, “Geoacoustic inversion using combustive sound source signals,” J.
Acoust. Soc. Am. 124, EL150 (2008)
Y-M Jiang, N. R. Chapman, M. Badiey, “ Quantifying the uncertainty of geoacoustic parameter estimates for the New Jersey shelf by
inverting air gun data,” J. Acoust. Soc. Am. 121, 1879-1894 (2007)
Modeling: Next steps
→ Creating 3D soundspeed profile requires interpolation from
various moorings and sensors and code modification
Conclusions & Future Work
R/V Sharp datasets
• Wealth of data from over 50 events across different bearings and
ranges
Events 44, 46, 47
• Provide evidence of refraction – and ‘ramping’ of intensity
measurements before arrival of IW
• Provide insight into depth dependence of intensity fluctuations
associated with (or lack of) warm water bottom intrusions
Modeling
• Simple 3D model shows similar trends to measured data
• Next steps to include measured data to better portray actual
environment
Thank you