November 4, 2010

1. Passive Acoustics • Brian Polagye, Chris Bassett, and Jim Thomson • University of Washington • Northwest National Marine Renewable Energy Center • New Environmental Technologies • Renewable Ocean Energy and the Marine Environment November 4, 2010

2. Need for New Environmental Technologies • Passive Acoustics • Introduction • Ambient Noise • Environmental Effects

3. Marine Energy Development • Uncertainty around the potential environmental effects of marine energy poses a barrier to development • Consensus that well-monitored pilot projects are a first step in reducing environmental uncertainty Courtesy of Marine Current Turbines

4. Pilot Monitoring: Wish List • Monitor the full range of potential stressor (e.g., noise) and receptor (e.g., marine mammal) interactions • Discriminate changes caused by marine energy pilot projects from large natural and anthropogenic variability • Robust, species specific identification • Provide information for decision making in real time • Monitor over a range of time scales (seconds to years) and length scales (cm to km)

5. Pilot Monitoring: Reality • Resources are scarce and monitoring needs must be prioritized based on risk • Some interactions will not be measurable at the pilot scale • Conditions at marine energy sites preclude or complicate many conventional methods • Integrating multiple, rich data streams is a major software challenge

6. Need for New Environmental Technologies • Passive Acoustics • Introduction • Ambient Noise • Environmental Effects

7. Passive Acoustics • Broadband noise • Existing, ambient noise • Noise from marine energy projects • Marine mammal echolocation • Species specific • Presence or absence Mature Technology, New Applications

8. Recording Hydrophone Loggerhead DSG • Deployments for three months at a time on seabed • Sample ambient noise • 1% duty cycle • 20 – 40,000 Hz

9. Need for New Environmental Technologies • Passive Acoustics • Introduction • Ambient Noise • Environmental Effects

10. Ambient Noise Sources

11. Ambient Noise Characteristics

12. Ambient Noise Variability What is the context for this variability?

13. Establishing Context: Shipping f s f f f f s f f f f f f f Automatic Identification System (AIS)

14. Establishing Context: Currents Acoustic Doppler Current Profiler (ADCP)

15. Measuring Noise in Strong Currents • When currents exceed 1 m/s, elevated, broadband noise masks other sources • Two contributors to this increase • Propagating noise • Pseudo-noise and self-noise • When currents exceed 1 m/s, most hydrokinetic turbines begin to operate Bassett et al., Characteristics of underwater ambient noise at a proposed tidal energy site in Puget Sound, MTS/IEEE Oceans 2010, Seattle, WA, September 20-23.

16. Need for New Environmental Technologies • Passive Acoustics • Introduction • Ambient Noise • Environmental Effects

17. Source-specific Received Levels

18. Evaluating Sound Transmission Loss Distance from source Source level at 1m RL = 179 – 18.4 log10(d) Received level Transmission loss coefficient

19. Estimated Project Noise • Two turbines • Source level for each turbine = 160 dB re 1 µPa at 1 m • Sources are incoherent • Same transmission loss as noise from ferry 0.5 km 1.0 km

20. Conclusions • Passive acoustics are a powerful tool for evaluating and monitoring acoustic effects of marine energy projects • Most effective when combined with additional tools to establish context

21. Thank You • More information available at: • http://depts.washington.edu/nnmrec