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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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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
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
echolocation clicks in killer whales
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…
killer whale audiogram
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
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
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
vessels measured
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

even 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

a killer whale echolocation click

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?!

vessels vs click vs audiogram

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
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
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
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
acknowledgements
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
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