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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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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


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


  • Spot the Orca


    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…


    2 orcas in captivity

    Attached probes to melon

    Measured ABR

    Most sensitive

    18-42 kHz

    Simplified from Szymanski et al. 1999

    Killer whale audiogram


    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?


    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


    Sample sites

    Study site


    Materials


    Sampling


    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


    Results


    More Results


    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


    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?!


    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!


    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


    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?


    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


    If we can lower noise of this


    And better understand this


    Then we can minimise impact on this


    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


    Questions?


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