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18 months of ambient underwater sound levels in Haro Strait, Puget Sound. Val Veirs Colorado College Colorado Springs, CO, [email protected] Scott Veirs Beam Reach marine science and sustainability school Seattle, WA, [email protected]. - PowerPoint PPT Presentation
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Val Veirs
Colorado College
Colorado Springs, CO, [email protected]
Scott Veirs
Beam Reach marine science and sustainability school
Seattle, WA, [email protected]
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