View
214
Download
1
Tags:
Embed Size (px)
Citation preview
Listening to the Sound: Ambient Noise in Admiralty Inlet
Motivation
• Study ambient noise and identify sources
• Results used by regulators in permitting process
Site
• Admiralty Inlet b/w
Port Townsend and
Whidbey Island
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
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
Data Processing Basic Algorithm
• Raw voltage data is tapered
• FFT on tapered data
• FFT output to power spectral density
• Apply calibration curve
• Ensemble averages
Recording Hydrophone Results
• Spectra chosen to represent different acoustic conditions at the site.
Recording Hydrophone Results• Spectrograms combine data in from individual spectra into a time series.
Other ship trafficFerry crossings
June 15th, 2009 Spectrogram
Recording Hydrophone Results• Sound Pressure Level (SPL) is obtained by integrating under the
PSD curve
June 15th, 2009 SPL Time Series
Recording Hydrophone Results• Cumulative Probability Density Function for May-August mobile hydrophone
deployment
Recording Hydrophone Results• SPL and velocity time series data for May-August deployment
Recording Hydrophone Results• SPL and depth averaged velocity time series for May 25th
Recording Hydrophone Results• SPL vs. depth averaged velocity. Error bars represent two std. deviations.
•Error bars represent two standard deviations.
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.
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.
Mobile Hydrophone Results• Selected spectra demonstrate different conditions:- Survey 10: Recreational boat near site (closest during 25m survey)- Survey 7: Quiet conditions
Mobile Hydrophone Results• Mobile hydrophone survey map
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
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
Ongoing Analysis
• Study feasibility of using the recording hydrophone in detecting cetacean vocalizations
Acoustic ReleaseExample Orca Vocalization
Acknowledgements
• Project funding provided by SnoPUD
• Joe Talbert for his fantastic equipment engineering
• Everybody in the CEE EFM lab
• Dr. Thomson and Dr. Polagye