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Passive Acoustic Monitoring for Tidal Energy Projects. Brian Polagye , Chris Bassett, and Jim Thomson University of Washington Northwest National Marine Renewable Energy Center. Ecological and Environmental Monitoring April 7, 2011. Evaluating Acoustic Effects.

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Passive Acoustic Monitoring for Tidal Energy Projects

Brian Polagye, Chris Bassett, and Jim Thomson

University of Washington

Northwest National Marine Renewable Energy Center

Ecological and Environmental Monitoring

April 7, 2011


Evaluating Acoustic Effects

Marine Mammal Behavioral Response to Sound

Sound Received by Marine Mammal

Context for Received Sound

Individual Life History

  • Sound generated by turbine

  • Site-specific sound propagation

  • Marine mammal hearing sensitivity

  • Ambient noise from other sources

  • Marine mammal activity state

  • Exposure to similar sounds


Quantifying Sound from Turbines

Nearby shipping

  • OpenHydro turbine (6 m diameter)

  • Drifting EARs data collection

  • Compare drift series to identify turbine-specific features

Bedload transport

AHD at fish farm

Common spectral peaks

(100 Hz – 3 kHz)

Data collected by Scottish Association of Marine Sciences


Marine Mammal Hearing Sensitivity

Turbine Noise

Southall et al. (2007) Marine mammal exposure criteria


Implication for Received Levels

Broadband Levels

Mid-frequency Cetaceans

4x reduction in area ensonified to 120 dB


Stationary Hydrophone Measurements

Loggerhead DSG

  • Autonomous hydrophone (32 GB capacity)

  • 80 kHz sampling

  • 2% duty cycle for 3 months


Temporal and Spatial Variability

Hydrophone Deployments

Cumulative Probability Density

Temporal variability dominates over spatial variability


Vessel Traffic Monitoring with AIS

  • Automatic Identification System (AIS) transponders required on all vessels greater than 300 tonnes gross weight and passenger vessels

  • Continuous data collection and archiving


Data Assimilation

Vessel Proximity

Noise Correlation

SPL (dB re 1 μPa)

Distance to closest vessel (km)

Vessel noise drives broadband noise levels

Source: Chris Bassett, forthcoming PhD dissertation



Sound during High Currents

Hydrophone Response

Current Velocity


Flow Shield Experiment

Hydrophone

with Flow Shield

Unshielded Hydrophone

High Velocity Region

High Porosity Foam

Hydrophone Element

Doppler Velocimeter

Sample volume aligned with hydrophone element

Quiescent Region

Hydrophone Pressure Case

Source: Chris Bassett, forthcoming PhD dissertation


Pseudo-Sound Identification

Unshielded Hydrophone

Hydrophone with

Flow Shield

Source: Chris Bassett, forthcoming PhD dissertation


Propagating Sound during High Currents

  • Bedload transport

    • Elevated noise at 5-50 kHz

    • Consistent with size of gravel and shell hash observed during ROV surveys; O(1 cm)

  • Turbulent flow over rough surfaces

    • Potential contribution from advected turbulence

    • Cannot measure velocity fluctuations directly at frequencies of interest (e.g., > 300 Hz)

(Hz)

(Thorne, 1986)

Source: Chris Bassett, forthcoming PhD dissertation


Measuring Noise from Tidal Turbines

Long-term, low-intensity monitoring

Short-term, spatial characterization


Thank You

  • This material is based upon work supported by the Department of Energy and Snohomish County PUD under Award Number DE-0002654.

Joe Talbert for keeping all equipment in working order.

Sam Gooch, Joe Graber, and Alex DeKlerk for helping turn around instrumentation.

Captains Andy Reay-Ellers for piloting skills during instrumentation deployment.


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