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