I usually say that 20 ships per day transit Haro Strait, but this is the first time I’ve seen a sound budget estimate from Jeff Nystuen’s data. This article quotes him as saying that ships dominate the sound budget, making noise about 60% of the time his PALs were deployed. That’s pretty consistent with 20 ships per day, each taking about 40 minutes to pass by, acoustically.
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Devices Tease Out Individual Sounds From Underwater Racket
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| ScienceDaily (Feb. 27, 2006) |
| In order to determine the sound “budgets” for different ecosystems, Nystuen and his team use what they call PALs, short for Passive Aquatic Listeners, designed and built at the Applied Physics Laboratory. Moored to the seafloor by long lines, PALs are submerged tens to thousands of meters below the surface and are set to listen for a few seconds every few minutes. |
| “Those are the two parts of a sound budget, the distribution of different sound sources as a percentage of time and the relative loudness,” he says. |
Sixty percent of the time, Haro Strait’s sound budget is dominated by shipping noise, Nystuen has found. It’s also heavily used by killer whales. “If the food is there, do the orcas care?” he asks. “That’s one for the biologists to determine.” |
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