Val Veirs Colorado College Colorado Springs, CO, Scott Veirs Beam Reach marine science and sustainability school Seattle, WA, 18 months of ambient underwater sound levels in Haro Strait, Puget Sound

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

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

Haro Strait Sound Sources Large Commercial Vessels Speedboats Orcas Harbor Seals Washington State Ferry Waves and Wind Odd Unique Sound Sources SonarWhat? ? At night ?

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

Hydrophone recording system Hydrophones: ITC-4066 Bandwidth: 100Hz – 15kHz Digitizing rate: 44,100 sec -1 Averaging time: 2 seconds Reporting interval: 30 minutes 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

24 hrs 24 hours of ambient sound in Haro Strait

Monthly Pattern of Ambient SPL June 2004 – November 2005

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

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

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

Winter ambient sound Jan 11 – Jan 13, am8 pm8 am DayNight 1/11 1/12 1/13 ~ 20 Large Commercial Ships Pass Each Day

8 am8 pm8 am DayNight 7/3 7/4 7/5 7/6 Commercial ships dominate at nightRecreational boats dominate during day Jul 03 – Jul 06, 2004 Summer ambient sound

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

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

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  Pa 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