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Acoustics of the Puget Sound

Acoustics of the Puget Sound. Michael Greiner Physics 536 University of Washington, March 2019. Puget Sound. Image Credit: Puget sound institute. Home to a huge wide variety of marine life Marine invertebrates and shellfish Salmon and other fish species Marine mammals Seals

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Acoustics of the Puget Sound

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  1. Acoustics of the Puget Sound Michael Greiner Physics 536 University of Washington, March 2019

  2. Puget Sound Image Credit: Puget sound institute Home to a huge wide variety of marine life • Marine invertebrates and shellfish • Salmon and other fish species • Marine mammals • Seals • Sea Lions, (Stellar and California) • Harbor porpoise • Minke, Humpback, Grey, and other whales • Endangered Southern Resident Killer Whale population Image credit: Metro Field Guide Img: David Suzuki Image credit: Alaska DFG

  3. Large metropolitan area Recreational Marine traffic Washington State Ferry System Second largest in the world Deep Draft Vessel Traffic Container ships Oil tankers Image credit Wikipedia Image: workboat.com Image: Spectrum.ieee.org

  4. Ambient noise from natural sources • Earthquakes < 100 Hz • Wind and waves 100 Hz - 10 kHz • Rain 12 kHz - 21 kHz • Marine Life • Marine invertebrates 2 kHz - 5 kHz • Marine mammal vocalization 10 Hz - 200 kHz Image: Pixels.com Image: Thomas Dutour Image: abc.net.au Image: folio.ca

  5. Anthropogenic Sound Sources: • Explosives • Seismic exploration, airgun arrays • Active sonar • Acoustic deterrent devices • Industrial Activities (pile driving) • Ships Image: Researchgate.net Image: csmarine.com

  6. Anthropogenic Sound Sources: Hildebrand, John A. (2009)

  7. How do we measure sound in Water? Hydrophones • Measure Sound Pressure Levels (SPL) in dB • SPL (dB) = 10log10 (p2/pref2) • Pref in water is 1 μPa • in air pref is 20 μPa Image: rtsys.eu

  8. Example: Admiralty Inlet Study conducted to investigate ambient noise levels for a proposed underwater turbine project. Noises detected were sound and pseudo sound Pseudo sound caused by turbulent water moving passed the hydrophone (much like rustling of wind in your ears on a windy day) How to eliminate contribution of pseudo sound to sound level measurements?

  9. Two Hydrophones! Using multiple hydrophones allows for multiple recordings of the same ambient noise. Compare the recordings and run correlation analysis between the two recordings. The pseudo sound will have very low correlation since it is random in nature The propagating sound will have high correlation because both hydrophones are recording the same SPLs

  10. Example Data Collection: Admiralty Inlet Images courtesy of google maps

  11. Example Data Collection: Admiralty Inlet Estimated source levels (.02-30 kHz) based on received levels for selected marine traffic transiting Admiralty Inlet in 2011 Bassett, Christopher, et al 2012

  12. Ship noise Primarily Cavitation of propeller https://www.youtube.com/watch?v=S8Jd4wnbX_Q • Broadband noise due to bubble collapse • Tonal components related to blade passage frequency Image credit: Petr Dalik Image credit: Nord Lock

  13. Marine mammal sound production Southern Resident Killer Whale vocalization https://www.youtube.com/watch?v=xmWuAm6420A Produce a variety of clicks and whistles used for communication and echolocation

  14. Struggling orca population Orcas must increase their call amplitude in response to vessel noise • S1 whale calls recorded with a background noise level of 100 dB • S1 call recorded in a background noise level of 115 dB Noise level attributed to vessel traffic in the area Holt et al 2008

  15. Southern Resident Orca Whale Recovery Gov. Jay Inslee announced investment of $1.1 Billion to help the Orca population • Increase abundance of Chinook Salmon • Decrease disturbance posed by vessel traffic • Reducing toxic pollutants • Ensure adequate funding for recovery efforts moving forward

  16. References: • Bassett, Christopher, et al. "A vessel noise budget for Admiralty Inlet, Puget Sound, Washington (USA)." The Journal of the Acoustical Society of America 132.6 (2012): 3706-3719. • Dahl, Peter H., et al. "Underwater ambient noise." Acoustics Today 3.1 (2007): 23-33. • Hildebrand, John A. "Anthropogenic and natural sources of ambient noise in the ocean." Marine Ecology Progress Series395 (2009): 5-20. • Holt, Marla M., et al. "Speaking up: Killer whales (Orcinus orca) increase their call amplitude in response to vessel noise." The Journal of the Acoustical Society of America 125.1 (2009): EL27-EL32. • Southall, Brandon L., et al. "Underwater Noise from Large Commercial Ships—International Collaboration for Noise Reduction." Encyclopedia of Maritime and Offshore Engineering (2017): 1-9.

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