Mid to High Frequency (1-20 kHz) Acoustics
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Mid to High Frequency (1-20 kHz) Acoustics at the Central Area, August 9-20. Applied Physics Laboratory University of Washington Peter H. Dahl, Jee Woong Choi.

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Mid to High Frequency (1-20 kHz) Acoustics at the Central Area, August 9-20

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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

Applied Physics Laboratory

University of Washington

Peter H. Dahl, Jee Woong Choi

Science measurement goal: measure contemporaneously MF acoustics and influencing environmental scales for ocean acoustic modeling and interpretation

  • 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


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

APL LEAR Deployments

SMALLER SCALE VIEW

0.5

0

WHOI environmental mooring

-0.5

U-Miami

wave buoy

-1

MORAY 1+ VLA/HLA Receiving

Array

-1.5

Y (km)

-2

500 m

APL-UW wave buoy

-2.5

Track of the R/V Endeavor

for internal wave & acoustic

propagation study

-3

Ship-deployed source location

(via precise positioning of R/V Knorr)

-3.5

-4

-0.5

0

0.5

1

1.5

2

2.5

X (km)


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

Shark

500 m

50 m

100 m

200 m

300 m

500 m

300o

1000 m

14

U Miami

1000 m

10

6

2

M1+

15

11

7

3

1

5

9

13

A2

A1

1000 m

500 m

4

8

12

Basic Layout for MF measurements about

the MORAY 1+ VLA/HLA system

16

B1

KEM 1000

B2


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

0m

50m

100m

200m

300m

25m

40m

80m

50m

A B C D E F G H

X

Y

BOTTOM REFLECTION

X  Y : size of 1st Fresnel zone (m)


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

SD: 40 m

RD: 25 m

0

0.4

10

20

30

40

50

MF output

(8-16 kHz)

60

70

-0.4

0

20

40

60

80

10

120

140

160

180

200

100

150

200

250

TIME (ms)

RANGE (m)

SD: 40 m

RD: 50 m

0.4

0

10

20

30

40

50

MF output

(8-16 kHz)

60

70

-0.4

0

20

40

60

80

10

120

140

160

180

200

100

150

200

250

TIME (ms)

RANGE (m)

C5 position (200 m range)


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

SD: 40 m

RD: 25 m

0.5

0

10

20

30

40

50

60

70

-0.5

80

0

50

100

150

200

250

300

180

200

220

240

260

280

300

320

TIME (ms)

RANGE (m)

SD: 40 m

RD: 50 m

0

0.5

10

20

30

40

50

60

70

80

-0.5

0

50

100

150

200

250

300

180

200

220

240

260

280

300

320

RANGE (m)

TIME (ms)

C13 position (300 m range)


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

20

20

1 kHz

10 kHz

14

15

15

10

10

10

BOTTOM LOSS

5

5

6

0

0

2

start

-5

-5

M1+

15

11

7

3

1

5

9

13

10

20

40

60

10

10

10

10

10

30

30

30

30

30

30

50

50

50

50

50

50

70

70

70

70

70

70

20

40

60

4

20

20

3 kHz

14 kHz

8

15

15

12

10

10

BOTTOM LOSS

5

5

16

0

0

-5

-5

20

40

60

20

40

60

20

20

6 kHz

20 kHz

15

15

10

10

BOTTOM LOSS

5

5

300o

0

0

-5

-5

20

40

60

20

40

60

GRAZING ANGLE (deg.)

GRAZING ANGLE (deg.)

C1  C13 direction


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

14

20

20

1 kHz

10 kHz

15

15

10

10

10

BOTTOM LOSS

6

5

5

2

start

0

0

M1+

15

11

7

3

1

5

9

13

10

10

10

10

10

30

30

30

30

30

30

50

50

50

50

50

50

70

70

70

70

70

70

-5

-5

10

4

20

40

60

20

40

60

8

20

20

3 kHz

14 kHz

15

15

12

10

10

BOTTOM LOSS

16

5

5

0

0

-5

-5

20

40

60

20

40

60

20

20

6 kHz

20 kHz

15

15

10

10

BOTTOM LOSS

300o

5

5

0

0

-5

-5

20

40

60

20

40

60

GRAZING ANGLE (deg.)

GRAZING ANGLE (deg.)

C1  C13 direction

C2  C14 direction


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

Knorr move out at 0.1 m/s Continuous Angle Study Range: 50-300 m

C2  C14

C1  C13

50 m

250 m

Time (ms)

C3  C15

C4  C16


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

20

2 kHz

15

10

BOTTOM LOSS (dB)

5

0

-5

10

20

30

40

50

60

70

GRAZING ANGLE (deg.)

M1-M13 direction

M2-M14 direction

20

4 kHz

15

10

BOTTOM LOSS (dB)

5

0

-5

10

20

30

40

50

60

70

GRAZING ANGLE (deg.)

Geoacoustic

model

for the site

PE-derived bottom loss (Seattle 06 meeting)

Water

~1485 m/s

1600 m/s

80 m

80.2 m

1720 m/s

81 m

1560 m/s

84.9 m

1750 m/s

95 m

Half space

1900 m/s


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

Studies on Sea Surface Boundary Effects


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

Wave Conditions 10 August

LF (swell) from the South

HF (wind waves) from the East


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

Shark

500 m

50 m

100 m

200 m

300 m

500 m

300o

1000 m

14

U Miami

1000 m

10

6

2

M1+

15

11

7

3

1

5

9

13

A2

A1

1000 m

500 m

4

8

12

16

B1

DIFFERENT PROPAGATIONDIRECTIONS THROUGH THE DIRECTIONAL WAVE FIELD

KEM 1000

B2


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

Knock Down of Horizontal Spatial Coherence at High Sea State

Horizontal Coherence

Vertical Coherence

15 AUG 12m/s

Coherence Magnitude

9 AUG 4m/s

kD/2p

kD/2p


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

Energy loss due to near surface bubbles for single surface

interaction at grazing angle 15o

(Preliminary results—heavy averaging)

Very interesting applied and basic implications….

> 10 kHz, ~3 dB

Loss (dB)

< 10 kHz, ~0 dB

Frequency (kHz)


Mid to high frequency 1 20 khz acoustics at the central area august 9 20

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 over

LF-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 to

kH<< 1 roughness


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