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Tim Hunt Beam Reach Marine Science and Sustainability School Fall 2007 - beamreach/071

I nvestigating high frequency underwater vessel noise and potential masking of killer whale echolocation clicks. Tim Hunt Beam Reach Marine Science and Sustainability School Fall 2007 - beamreach.org/071 Flinders University of South Australia. Introduction.

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Tim Hunt Beam Reach Marine Science and Sustainability School Fall 2007 - beamreach/071

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  1. Investigating high frequency underwater vessel noise and potential masking of killer whale echolocation clicks Tim HuntBeam Reach Marine Science and Sustainability SchoolFall 2007 - beamreach.org/071 Flinders University of South Australia

  2. Introduction • The Southern Resident Killer Whale • Endangered • Increase in WW boats over the years • ‘98-’05 consistently 20 vessels within ½ mile radius • Erbe (2002) - underwater noise study of WW boats • My study expand on aspects of this – boater cooperation! • Look at specific vessel types using HF hydrophone • Sample up to 30 kHz at 44.1k sampling rate - HF samples up to 90 kHz at 192k sampling rate WOW! • Not done before measuring vessel noise new & novel! • Echolocation clicks in these higher frequencies • Compare with boat noise to infer possible masking? • Relate to County Law and WW guidelines

  3. Spot the Orca

  4. Echolocation clicks in killer whales • What is an echolocation click? • What is it used for? • What does it sound like? • High frequency, range up to 80 kHz • Need a device to sample up to these high frequencies…

  5. 2 orcas in captivity Attached probes to melon Measured ABR Most sensitive 18-42 kHz Simplified from Szymanski et al. 1999 Killer whale audiogram

  6. Questions posed • Is a vessel cruising at high speeds (>18 knots) at 400m “louder” that a vessel slow motoring at low speeds (5-8 knots) at 100m? • Is there is a difference in frequency spectrum levels between different vessel propulsion types? • To what degree, if at all, do different vessel types mask echolocation clicks?

  7. Methods • Two speeds, two distances (relates to SJ County Law and BWW guidelines) • Slow Motor (SM) = speed of 5-8 knots • When within 400m of whales • Cruise (C) = 18-25 knots • When further than 400m • Test SM and C at 100m and 400m • Record echolocation clicks

  8. Sample sites Study site

  9. Materials

  10. Sampling

  11. Vessels measured • Business names kept anonymous, vessel classification based on propulsion system • Twin Inboard 400HP BioDiesel • Twin Outboard 150HP • Surface Piercing • Twin Inboard Diesel • Jet Drive • Also measured Gato Verde catamaran, Washington State Ferry, cargo ship and dinghy

  12. Results

  13. More Results

  14. Even more results • No sig. difference b/w SM 100m & C 400m • 3/5 vessels had difference in RL of 10 dB or greater (C 400m > SM 100m) • Twin OB 150HP opposite • Surface Piercing 1dB difference

  15. Sounds above echo, clicks masked Sounds below echo, clicks heard A killer whale echolocation click What in the bloody hell do all these lines mean?!

  16. 2 vessels below echo All vessels above echo Both 115.5 dB Vessels vs. click vs. audiogram MASKING Higher spectrum level = higher mean RL? NO!

  17. Discussion • Peaks in Jet Drive vessel, & Twin IB 400HP BioDiesel. Mmm…. • What is a significant dB difference? • 6 dB = twice as loud in human ear • Gato Verde – EM vs G, just propeller noise? • Echolocation click mean • Bimodal distribution 10-50 kHz • Similar to Au et al. 2003

  18. Things to think about • KW Audiogram – is it representative of wild orcas? • Individual tested reportedly partially deaf • Busy day in the Haro Strait - individual vessel noise might be indistinguishable to an orca • Hard to quantify difference in vessel type • Can’t really say one is better/worse than another • Can’t really say one is having more/less effect on echolocation • Personal observations – orcas swimming under ferries & riding bow wave of cargo ship • Does noise really bother them?

  19. Improvements/Future research • Make sample size bigger! • Sample vessels on separate days • More clicks, perhaps infer distance? • Measure vessels at more distances, build database, compare, infer, legislate? • Engine noise? Propeller noise? Combination? • Test these to aid in minimising underwater noise • More research = better understanding

  20. If we can lower noise of this

  21. And better understand this

  22. Then we can minimise impact on this

  23. Acknowledgements • Beam Reach and all the crew • Boat operators for driving-by • Whale watch operators for the good times on the radio • Team VaTo for putting up with my singing • Flight Of The Conchords for musical comic relief during times of hardship

  24. Questions?

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