Val Veirs

Colorado College

Colorado Springs, CO, vveirs@coloradocollege.edu

Scott Veirs

Beam Reach marine science and sustainability school

Seattle, WA, scott@beamreach.org

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 siteOVAL: 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 SourcesSonar What?

? At night ?

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

Hydrophone recording systemHydrophones: 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 SPLJune 2004 – November 2005

Monthly Average Sound Levels - June 2004 through November 2005

114

114.5

115

115.5

116

116.5

117

117.5

118d

B r

e 1

mP

a (1

00 H

z -

15 k

Hz)

Error bars are standard error of the mean for each hour

Diurnal ambient sound pressure levelJune 2004 – November 2005

Comparison of Sound Levels between Summer (Jul-Aug) and Non-Summer(Oct-April)

112

113

114

115

116

117

118

119

120

121

0 5 10 15 20 25

Hour in Day

dB

re 1

mic

roP

a (

100 H

z -

20 k

Hz)

Non Summer

Summer

SPL by Day of Week, July-August 2005

115

115.5

116

116.5

117

117.5

118

1 2 3 4 5 6 7

Ambient SPL vs day of the week

Mon Tue Wed Thu Fri Sat Sun

Summer 2005

Percentage of Time Sound Level is Less than SPL

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

100.00 105.00 110.00 115.00 120.00 125.00 130.00 135.00

SPL (dB re 1 microPa)

Cu

mu

lati

ve P

erc

en

tag

e

Summer Day

Summer Night

Winter Average

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, 2005

8 am 8 pm 8 am

Day Night

1/11

1/12

1/13

~ 20 Large Commercial Ships Pass Each Day

8 am 8 pm 8 am

Day Night

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