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Long-Time Trends in Oceanic Ambient Noise along the Western North America Coast . Rex K. Andrew, Bruce M. Howe, James A. Mercer. Applied Physics Laboratory, University of Washington. Work sponsored by U.S. Office of Naval Research Code 321OA. History.

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long time trends in oceanic ambient noise along the western north america coast
Long-Time Trends in Oceanic Ambient Noise along the Western North America Coast

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

Applied Physics Laboratory, University of Washington

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

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

history
History
  • Wenz (1963-1966) 2 - 3 years of measurements over 10 Hz - 400 Hz
  • Burke et al (1982) 3 years of sonobuoy measurements in NE Pacific
  • Urick (1984) Several 1-year series
  • McCreery et al (1993) 1-year time series 0.4-30 Hz
  • Lynch et al (1993) 1-year series in Greenland Sea
  • Curtis, Howe & Mercer (1999) 2-year 1 - 500 Hz time series, 13 sites in N. Pacific
  • Andrew, Howe, Mercer & Dzieciuch (2002) 6-year, 10 – 100 Hz, one site, comparison against Wenz (30 years)
  • McDonald, Hildebrand & Wiggins (2006) 1 year, 10 – 500 Hz, one site, comparison against Wenz (40 years)

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

receiver systems
Receiver Systems

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

typical data acquisition system
Typical Data Acquisition System

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

ambient sound calibration
Ambient Sound Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site d
Site D

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site d calibration
Site D --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site d calibration1
Site D --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site d calibration2
Site D --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site d calibration3
Site D --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site f
Site F

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site f calibration
Site F --- Calibration
  • McDonald et al, JASA120(2) August 2006
  • Autonomous seafloor recording package (ARP)
  • @ site F for November 2003 – March 2004
  • 30 to 50 Hz PSD levels are 10 – 12 dB higher than Wenz literature (1960’s)
  • www.whaleacoustics.com

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site f calibration1
Site F --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site f calibration2
Site F --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site f calibration3
Site F --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

sites g and h
Sites G and H

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site g h calibration
Site G & H --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

sites g h calibration
Sites G & H --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site g calibration
Site G --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site h calibration
Site H --- Calibration

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

historical comparisons
Historical Comparisons
  • Investigate recent decadal trend in “distant shipping”
    • Shipping: loudest 16 – 32 Hz, up to 50 or 60 Hz
    • 60 Hz AC contamination is ubiquitous
    • Baleen whale “noise” dominates 16 – 20 Hz
  • Synthesize one-third octave (OTO) levels
  • Extract monthly medians (yields reduced time series)
  • Estimate periods of dominant baleen influence at 16 Hz, 20 Hz
  • Tease out estimate of “distant shipping noise trend” at 31 Hz
  • Compare recent decadal trend with 1960’s point measurements

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

psd level time series model i
PSD Level Time Series Model - I
  • model level versus time as

where

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

psd level time series model ii
PSD Level Time Series Model - II
  • 16, 20 Hz: Unconstrained least-squares optimization on baleen amplitudes, durations, center times, slope and intercept of underlying “trend line”
  • 31 Hz: Unconstrained least-squares “Bayesian” optimization of slope and intercept of underlying “trend line”, with priors on baleen influence:
  • Amplitudes: exponential
  • Durations: erlang
  • Center Times: gaussian

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

baleen whales site f
Baleen Whales: Site F

(unconstrained optimization)

16 Hz

20 Hz

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site d shipping trend 31 hz
Site D: Shipping Trend – 31 Hz

(Bayesian solution)

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site f shipping trend 31 hz
Site F: Shipping Trend – 31 Hz

(Bayesian solution)

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site g shipping trend 31 hz
Site G: Shipping Trend – 31 Hz

(Bayesian solution)

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

site h shipping trend 31 hz
Site H: Shipping Trend – 31 Hz

(Bayesian solution)

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

comparison all coastal systems
Comparison: All Coastal Systems

Ross: Mechanics of Underwater Noise (1976)

& Acoustics Bulletin (1993)

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

summary
Summary
  • Reasonable calibrations for 4 coastal systems now available
  • Fin and blue whales rule!
  • Simple model fit to decadal time series @ 31 Hz
  • 40 year change: +10 dB increase
  • “Dynamic” contribution to Ross figure
  • Decadal: Sites D & F: 0.05 to 0.22 dB/year
  • Decadal: Sites G & H: less informative (no increase?)

Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA