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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. History.

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

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  1. 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

  2. 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

  3. Receiver Systems Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  4. Typical Data Acquisition System Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  5. Ambient Sound Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  6. Site D Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  7. Site D --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  8. Site D --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  9. Site D --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  10. Site D --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  11. Site F Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  12. 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

  13. Site F --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  14. Site F --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  15. Site F --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  16. Sites G and H Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  17. Site G & H --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  18. Sites G & H --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  19. Site G --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  20. Site H --- Calibration Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  21. 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

  22. PSD Level Time Series Model - I • model level versus time as where Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  23. 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

  24. Baleen Whales: Site F (unconstrained optimization) 16 Hz 20 Hz Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  25. Site D: Shipping Trend – 31 Hz (Bayesian solution) Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  26. Site F: Shipping Trend – 31 Hz (Bayesian solution) Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  27. Site G: Shipping Trend – 31 Hz (Bayesian solution) Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  28. Site H: Shipping Trend – 31 Hz (Bayesian solution) Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  29. Comparison: All Coastal Systems Ross: Mechanics of Underwater Noise (1976) & Acoustics Bulletin (1993) Pacific Rim Underwater Acoustics Conference  October 2007: Vancouver CA

  30. 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

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