Long-Time Trends in Oceanic Ambient Noise along the Western North America Coast

Pacific Rim Underwater Acoustics ConferencePacific Rim Underwater Acoustics Conference October 2007: October 2007: Vancouver CA Vancouver CA

Long-Time Trends in Oceanic Long-Time Trends in Oceanic Ambient Noise along the Ambient Noise along the

Western North America Coast Western North America Coast

Rex K. Andrew, Bruce M. Howe, James A. Mercer

Work sponsored by U.S. Office of Naval Research Code 321OA

Applied Physics Laboratory, University of Washington


HistoryHistory

• Wenz (1963-1966) 2 - 3 years of measurements over 10 Hz - Wenz (1963-1966) 2 - 3 years of measurements over 10 Hz - 400 Hz400 Hz

• Burke et al (1982) 3 years of sonobuoy measurements in NE Burke et al (1982) 3 years of sonobuoy measurements in NE PacificPacific

• Urick (1984) Several 1-year seriesUrick (1984) Several 1-year series

• McCreery et al (1993) 1-year time series 0.4-30 HzMcCreery et al (1993) 1-year time series 0.4-30 Hz

• Lynch et al (1993) 1-year series in Greenland SeaLynch et al (1993) 1-year series in Greenland Sea

• Curtis, Howe & Mercer (1999) 2-year 1 - 500 Hz time series, 13 Curtis, Howe & Mercer (1999) 2-year 1 - 500 Hz time series, 13 sites in N. Pacificsites in N. Pacific

• Andrew, Howe, Mercer & Dzieciuch (2002) 6-year, 10 – 100 Hz, Andrew, Howe, Mercer & Dzieciuch (2002) 6-year, 10 – 100 Hz, one site, comparison against Wenz (30 years)one site, comparison against Wenz (30 years)

• McDonald, Hildebrand & Wiggins (2006) 1 year, 10 – 500 Hz, McDonald, Hildebrand & Wiggins (2006) 1 year, 10 – 500 Hz, one site, comparison against Wenz (40 years)one site, comparison against Wenz (40 years)


Receiver SystemsReceiver Systems

220˚

220˚

230˚

230˚

240˚

240˚

250˚

250˚

20˚ 20˚

30˚ 30˚

40˚ 40˚

50˚ 50˚

D

F

G

H


Typical Data Acquisition Typical Data Acquisition SystemSystem

ArrayCable

to Shore

APLModem Running

AmplifierATOCFilter

& GainA/D

Sampling Interval: 5–6 minutes

Sample size: 170s

i686

Linux

removablehard drive

40 GB


Ambient Sound CalibrationAmbient Sound Calibration

FGGVGG

Pam( )

SSH f( )

TS( )f ADCFHpf ( )f

equalizer filter/gainacousticfield

A/DC

gainfixed

filteranti−alias

gaincorner frequency

filterequalizer

digitizedvoltage( bits )

attenuationvari−gain

prefiltershoresideamplifier&

transducerand


Site DSite D

220˚

220˚

230˚

230˚

240˚

240˚

250˚

250˚

20˚ 20˚

30˚ 30˚

40˚ 40˚

50˚ 50˚

D

F

G

H


Site D --- CalibrationSite D --- Calibration12229' 12228' 12227' 12226' 12225' 12224' 12223'

3619'

3618'

3617'

3616'

HLA

2,0001,000

meters

0

VLA Locations


Site D --- CalibrationSite D --- Calibration

0 10 20 30 40 50 60 70 80 90−50

−40

−30

−20

−10

0

10

frequency [Hz]

corr

ecti

on

fu

ncti

on

[d

B]

pop maxupper quartilemediantrimmed meanlower quartilepop min



Pam( )equalizer filter/gain

acousticfield

A/DCdigitizeddvoltage(bits)


transducerandcable

APL rack APL rack

CalibrationAuxiliary



fre

q [

Hz]

time [month/year]

Site d, median PSD removed

01/95 01/96 01/97 01/98 01/99 01/00 01/01 01/02 01/03 01/04 01/05 01/0610

20

50

100

200

500

level [dB]

−10

−5

0

5

10

15

20

25


Site FSite F

220˚

220˚

230˚

230˚

240˚

240˚

250˚

250˚

20˚ 20˚

30˚ 30˚

40˚ 40˚

50˚ 50˚

D

F

G

H


Site F --- Calibration Site F --- Calibration

• McDonaldMcDonald et al, JASA et al, JASA 120120(2) August (2) August 20062006

• Autonomous seafloor recording Autonomous seafloor recording package (ARP)package (ARP)

• @ site F for November 2003 – @ site F for November 2003 – March 2004March 2004

• 30 to 50 Hz PSD levels are 10 – 12 30 to 50 Hz PSD levels are 10 – 12 dB higher than Wenz literature dB higher than Wenz literature (1960’s) (1960’s)

• www.whaleacoustics.comwww.whaleacoustics.com


Site F --- Calibration Site F --- Calibration

101

102

60

65

70

75

80

85

90

95

100

105Comparison of systems, median December 2003 levels

Frequency [Hz]

Le

ve

l [d

B r

e 1

mPa2 /H

z]

APL system (+ offset)ARP


Site F --- CalibrationSite F --- Calibration


acousticfield



transducerandcable

APL rack APL rack

CalibrationAuxiliary


Site F --- Calibration Site F --- Calibration fr

eq

[H

z]

time [month/year]

Site f, median PSD removed

01/95 01/96 01/97 01/98 01/99 01/00 01/01 01/02 01/03 01/04 01/05 01/06 01/0710

20

50

100

200

500

level [dB]

−10

−5

0

5

10

15

20


Sites G and HSites G and H

220˚

220˚

230˚

230˚

240˚

240˚

250˚

250˚

20˚ 20˚

30˚ 30˚

40˚ 40˚

50˚ 50˚

D

F

G

H


Site G & H --- CalibrationSite G & H --- Calibration

10 20 50 100 200 500

60

65

70

75

80

85

90

frequency [Hz]

tran

sfe

r fu

nct

ion

(g

ain

) [d

B]

GEAGEBGECGED


Sites G & H --- CalibrationSites G & H --- Calibration


acousticfield



transducerandcable

APL rack APL rack


Site G --- CalibrationSite G --- Calibrationfr

eq

[H

z]

time [month/year]

Site g, median PSD removed

01/95 01/96 01/97 01/98 01/99 01/00 01/01 01/02 01/03 01/04 01/05 01/0610

20

50

100

200

500

level [dB]

−10

−5

0

5

10

15


Site H --- CalibrationSite H --- Calibrationfr

eq

[H

z]

time [month/year]

Site h, median PSD removed

01/95 01/96 01/97 01/98 01/99 01/00 01/01 01/02 01/03 01/04 01/05 01/0610

20

50

100

200

500

level [dB]

−10

−5

0

5

10

15


Historical ComparisonsHistorical Comparisons• Investigate recent decadal trend in “distant shipping” Investigate recent decadal trend in “distant shipping”

– Shipping: loudest 16 – 32 Hz, up to 50 or 60 HzShipping: loudest 16 – 32 Hz, up to 50 or 60 Hz

– 60 Hz AC contamination is ubiquitous60 Hz AC contamination is ubiquitous

– Baleen whale “noise” dominates 16 – 20 HzBaleen whale “noise” dominates 16 – 20 Hz

• Synthesize one-third octave (OTO) levelsSynthesize one-third octave (OTO) levels

• Extract monthly medians (yields reduced time series)Extract monthly medians (yields reduced time series)

• Estimate periods of dominant baleen influence at 16 Hz, 20 HzEstimate periods of dominant baleen influence at 16 Hz, 20 Hz

• Tease out estimate of “distant shipping noise trend” at 31 HzTease out estimate of “distant shipping noise trend” at 31 Hz

• Compare recent decadal trend with 1960’s point Compare recent decadal trend with 1960’s point

measurementsmeasurements


PSD Level Time Series Model - IPSD Level Time Series Model - I

• model level versus time asmodel level versus time as

x(t) = G( ) + bt + c + e(t)a jt - tsj

jSj=1

where

G(q) = e -q /2


PSD Level Time Series Model - PSD Level Time Series Model - IIII

• 16, 20 Hz: Unconstrained least-squares 16, 20 Hz: Unconstrained least-squares optimization on baleen amplitudes, durations, optimization on baleen amplitudes, durations, center times, slope and intercept of underlying center times, slope and intercept of underlying “trend line”“trend line”

• 31 Hz: Unconstrained least-squares “Bayesian” 31 Hz: Unconstrained least-squares “Bayesian” optimization of slope and intercept of underlying optimization of slope and intercept of underlying “trend line”, with priors on baleen influence: “trend line”, with priors on baleen influence:

Amplitudes: Amplitudes: exponentialexponential Durations: erlangDurations: erlang Center Times: gaussianCenter Times: gaussian


Baleen Whales: Site FBaleen Whales: Site F

0 500 1000 1500 2000 2500 3000 3500 4000 450075

80

85

90

95

time [yeardays re: 1994]

spe

ctr

al le

ve

l [d

B]

0 500 1000 1500 2000 2500 3000 3500 4000 4500−4

−3

−2

−1

0

1

2

3


err

or

[dB

]

16~Hz OTO dataLS Model

(unconstrained optimization)

0 500 1000 1500 2000 2500 3000 3500 4000 450075

80

85

90

95


spectr

al le

ve

l [d

B]

0 500 1000 1500 2000 2500 3000 3500 4000 4500−3

−2

−1

0

1

2

3


err

or

[dB

]

20~Hz OTO dataLS Model

16 Hz

20 Hz


Site D: Shipping Trend – 31 Site D: Shipping Trend – 31 HzHz

(Bayesian solution)

0 1000 2000 3000 4000 5000

88

90

92

time [yearday re: 1994]

leve

l [d

B r

e 1m

Pa2 /H

z in

OT

O b

an

d]

0 1000 2000 3000 4000 5000

88

90

92

1994 1996 1998 2000 2002 2004 2006


Site F: Shipping Trend – 31 Site F: Shipping Trend – 31 HzHz

(Bayesian solution)

0 1000 2000 3000 4000 5000

82

84

86


leve

l [d

B r

e 1m

Pa2 /H

z in

OT

O b

an

d]

0 1000 2000 3000 4000 5000

82

84

86

1994 1996 1998 2000 2002 2004 2006


Site G: Shipping Trend – 31 Site G: Shipping Trend – 31 HzHz

(Bayesian solution)

0 1000 2000 3000 4000 5000

81

83

85

87


leve

l [d

B r

e 1m

Pa2 /H

z in

OT

O b

an

d]

0 1000 2000 3000 4000 5000

81

83

85

87

1994 1996 1998 2000 2002 2004 2006


Site H: Shipping Trend – 31 Site H: Shipping Trend – 31 HzHz

(Bayesian solution)

0 1000 2000 3000 4000 5000

85

87

89


leve

l [d

B r

e 1m

Pa2 /H

z in

OT

O b

an

d]

0 1000 2000 3000 4000 5000

85

87

89

1994 1996 1998 2000 2002 2004 2006


Comparison: All Coastal Comparison: All Coastal SystemsSystems

Ross: Mechanics of Underwater Noise Ross: Mechanics of Underwater Noise (1976)(1976)

& Acoustics Bulletin (1993) & Acoustics Bulletin (1993)

1950 1960 1970 1980 1990 2000 2010

70

75

80

85

90

95

10

0

year

level [d

B r

e: 1mP

a2 /H

z in

OTO

ba

nd]

D

FG

H

D 31 HzF 31 HzG 31 HzH 31 Hz


SummarySummary

• Reasonable calibrations for 4 coastal systems now Reasonable calibrations for 4 coastal systems now availableavailable

• Fin and blue whales rule!Fin and blue whales rule!

• Simple model fit to decadal time series @ 31 HzSimple model fit to decadal time series @ 31 Hz

• 40 year change: +10 dB increase40 year change: +10 dB increase

• ““Dynamic” contribution to Ross figure Dynamic” contribution to Ross figure

• Decadal: Sites D & F: 0.05 to 0.22 dB/yearDecadal: Sites D & F: 0.05 to 0.22 dB/year

• Decadal: Sites G & H: less informative (no increase?)Decadal: Sites G & H: less informative (no increase?)

Long-Time Trends in Oceanic Ambient Noise along the Western North America Coast

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