1. NNMREC April 20, 2011 Ambient Noise in Admiralty Inlet Chris Bassett, Brian Polagye, and Jim Thomson University of Washington Northwest National Marine Renewable Energy Center NNMREC PI Update

2. NNMREC Recording Hydrophone Loggerhead DSG ParameterValue Sample Rate80 kHz Storage32 GB (Flash) Effective Sensitivity -165 dB re 1V/μPa Linear Response20 Hz – 40 kHz

3. NNMREC Ambient Noise Sources Bedload Transport Ship Average Conditions Quiet

4. NNMREC Ambient Noise Characteristics Cumulative Probability Density Hydrophone Deployments Temporal variability dominates over spatial variability

5. NNMREC Strong Currents Overnight Lull in Shipping First Run for Passenger Ferry Recording Hydrophone Automatic Identification System Doppler Profiler Establishing Context for Observations

6. NNMREC 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

7. NNMREC Data Assimilation SPL (dB re 1 μPa) Distance to closest vessel (km) Vessel ProximityNoise Correlation Vessel noise drives broadband noise levels Source: Chris Bassett, forthcoming PhD dissertation

8. NNMREC Sound during High Currents Hydrophone Response Current Velocity

9. NNMREC Flow Shield Experiment Hydrophone with Flow Shield Unshielded Hydrophone Doppler Velocimeter Sample volume aligned with hydrophone element High Velocity Region Quiescent Region High Porosity Foam Hydrophone Element Hydrophone Pressure Case Source: Chris Bassett, forthcoming PhD dissertation

10. NNMREC Pseudo-Sound Identification Unshielded Hydrophone Hydrophone with Flow Shield Source: Chris Bassett, forthcoming PhD dissertation

11. NNMREC 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

12. NNMREC Ambient Noise Summary  Ambient noise levels in Admiralty Inlet are high ―Mean broadband SPL ≈ 119 dB re 1 μPa (20 Hz – 30 kHz) ―Ambient noise exceeds NMFS marine mammal harassment threshold ≈50% of the time  Sound from shipping dominates ambient noise ―Will complicate turbine noise measurements  Measurements during strong currents are challenging ―Flow shields can significantly mitigate contamination by pseudo-sound ―Bedload transport likely contributes to high current noise budget

13. NNMREC Thank You This material is based upon work supported by the Department of Energy and Snohomish County PUD under Award Number DE-0002654 and the National Science Foundation Graduate Research Fellowship.  Joe Talbert for keeping all equipment in working order.  Sam Gooch, Joe Graber, and Alex DeKlerk for helping turn around instrumentation.  Captain Andy Reay-Ellers for piloting skills during instrumentation deployment.