18 months of ambient underwater sound levels in Haro Strait, Puget Sound

1. 18 months of ambient underwater sound levels in Haro Strait, Puget Sound Val Veirs Colorado College Colorado Springs, CO, vveirs@coloradocollege.edu Scott Veirs Beam Reach marine science and sustainability school Seattle, WA, scott@beamreach.org

2. Study siteOVAL: Orca Vocalization and Localization Vancouver Victoria Seattle A 4-hydrophone array is permanently deployed on the west side of San Juan Island in Haro Strait.

3. Haro Strait is Orca habitat Sighting data expressed in Orca sightings per day per square km Figure courtesy of Donna Hauser, University of Washington

4. Haro Strait Sound Sources ? At night ? • Large Commercial Vessels • Speedboats • Orcas • Harbor Seals • Washington State Ferry • Waves and Wind • Odd Unique Sound Sources Sonar What?

5. What is this very slowly moving vessel doing on April Fools Day, 2004?

6. Hydrophones: ITC-4066 Bandwidth: 100Hz – 15kHz Digitizing rate: 44,100 sec-1 Averaging time: 2 seconds Reporting interval: 30 minutes Hydrophone recording system • Reported for each interval: • Average received level over the 30 minute interval (dB re 1 micro Pa) • 2-second sound file (.wav) at beginning of each interval • 2-second file from sample with highest average sound pressure level • Histogram of 2-second average sound levels (900 samples) • Graph (.jpg) of sound pressure level over the previous 12 hours

7. 24 hrs 24 hours of ambient sound in Haro Strait

8. Monthly Pattern of Ambient SPL June 2004 – November 2005

9. Diurnal ambient sound pressure level June 2004 – November 2005 Error bars are standard error of the mean for each hour

10. Ambient SPL vs day of the week Summer 2005 Mon Tue Wed Thu Fri Sat Sun

11. Cumulative Distribution of Average SLP SPL is less than ~113 dB about 50% of the time during the winter and during summer nights The average SPL is less than ~113 dB about 10% of the time during summer days

12. Day Night 1/11 1/12 1/13 8 am 8 pm 8 am Winter ambient soundJan 11 – Jan 13, 2005 ~ 20 Large Commercial Ships Pass Each Day

13. Day Night 7/3 7/4 7/5 7/6 8 am 8 pm 8 am Jul 03 – Jul 06, 2004 Summer ambient sound Recreational boats dominate during day Commercial ships dominate at night

14. Spectrum Levels: Winter • In winter, there is little difference in spectral power between day and night across the frequency spectrum.

15. Spectrum Levels – Summer • In Summer, spectrum levels are ~5-10 dB higher during the day than at night at frequencies > ~1000 hz.

16. Conclusions • Large commercial ships are the dominant source of ambient noise in the Haro Strait during the day and the night in the winter. Average SPL = 113 dB re 1 mPa over 100 Hz-15 kHz bandwidth During the winter, the SPL is less than 112 dB 50% of the time Maximum average SPL = 144 dB • Recreational vessels make significant contributions to the noise budget during summer days. Increase in average SPL due to recreational vessels on summer days = ~5-10 dB This increase is in the “high frequency” regime: 1 kHz – 15 kHz During summer days, the average SPL is greater than the winter (and nighttime) average of 113 dB 90% of the daytime. This average daytime SPL is ~ 118 dB