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Listening to the Sound: Ambient Noise in Admiralty Inlet
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Motivation
• Study ambient noise and identify sources
• Results used by regulators in permitting process
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Site
• Admiralty Inlet b/w
Port Townsend and
Whidbey Island
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Data Collection
• Temporal Data-Three month sea
spider deployments
- Samples at 80 kHz.
• Spatial Data- Deployment from
R/V deck during cruises
-Samples at 400 kHz
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Typical Sources• G. Wenz, 1962 identifies
typical sources of ambient noise in deep water
• freq < 100 Hz: turbulent pressure fluctuations, seismic activity, explosions
• 10 – 10,000 Hz: ships, industrial activity
• 100 – 50,000 Hz: bubbles and spray, weather
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Data Processing Basic Algorithm
• Raw voltage data is tapered
• FFT on tapered data
• FFT output to power spectral density
• Apply calibration curve
• Ensemble averages
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Recording Hydrophone Results
• Spectra chosen to represent different acoustic conditions at the site.
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Recording Hydrophone Results• Spectrograms combine data in from individual spectra into a time series.
Other ship trafficFerry crossings
June 15th, 2009 Spectrogram
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Recording Hydrophone Results• Sound Pressure Level (SPL) is obtained by integrating under the
PSD curve
June 15th, 2009 SPL Time Series
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Recording Hydrophone Results• Cumulative Probability Density Function for May-August mobile hydrophone
deployment
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Recording Hydrophone Results• SPL and velocity time series data for May-August deployment
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Recording Hydrophone Results• SPL and depth averaged velocity time series for May 25th
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Recording Hydrophone Results• SPL vs. depth averaged velocity. Error bars represent two std. deviations.
•Error bars represent two standard deviations.
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Recording Hydrophone Results
Flood Ebb
Depth Ave.Velocity (m/s)
Total SPL (dB re 1 μPa)
Per. Noise(dB re 1 μPa)
Depth Ave. Velocity (m/s)
Total SPL (dB re 1 μPa)
Per. Noise(dB re 1 μPa)
0 - 0.5 112.8 ± 13.1 99.7 0 - 0.5 112.6 ± 13.3 99.3
0.5 - 1.0 115.7 ± 12.0 103.7 0.5 - 1.0 114.0 ±12.4 101.6
1.0 - 1.5 124.3 ± 10.8 113.5 1.0 - 1.5 118.7 ± 8.8 109.9
1.5 - 2.0 132.8 ± 8.3 124.5 1.5 - 2.0 126.5 ± 7.5 119.0
2.0 - 2.5 138.9 ± 6.9 132.0 2.0 - 2.5 133.1 ± 6.5 126.6
2.5 - 3.0 142.7 ± 3.8 138.9 2.5 - 3.0 138.1.6 ± 6.1 132.1
- - - 3.0 < 141.3 ± 4.1 137.2
• Permanent Noise Levels for depth averaged velocity bins.
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Mobile Hydrophone Surveys
• Surveys taken in concentric circles around site at 0m, 500m, 1000m, 1500m, 2000m, and 2500m
• Surveys taken a 3m, 25m, and 50m below the surface
• Purpose is to search for patterns in spatial variations near the site.
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Mobile Hydrophone Results• Selected spectra demonstrate different conditions:- Survey 10: Recreational boat near site (closest during 25m survey)- Survey 7: Quiet conditions
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Mobile Hydrophone Results• Mobile hydrophone survey map
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Conclusions
• Stationary Hydrophone Surveys• Stationary surveys demonstrate clear dependence on tidal currents• Anthropogenic noise (ship traffic) also causes regular increases in
spectral levels and SPLs
• Mobile Hydrophone Surveys• Mobile hydrophones show no spatial patterns• High resolution spectra and notes taken during surveys demonstrate
impact of known anthropogenic noise sources on the acoustic environment
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Ongoing Analysis• Study impact of turbulent pressure fluctuations (psuedo
sound) on recorded spectral levels
- This is also called “flow noise”
• Seasonal variations?• Use AIS to identify contributions from ship traffic
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Ongoing Analysis
• Study feasibility of using the recording hydrophone in detecting cetacean vocalizations
Acoustic ReleaseExample Orca Vocalization
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Acknowledgements
• Project funding provided by SnoPUD
• Joe Talbert for his fantastic equipment engineering
• Everybody in the CEE EFM lab
• Dr. Thomson and Dr. Polagye