Assessing Sonar Sound Levels from Commercial Ships
August 2021 — British Columbia, Canada
Client: Transport Canada Innovation Centre
A study of the occurrence of sonar sounds in acoustic data recorded in Georgia Strait and Boundary Pass up to October 2019. Sonars were detected in 1.3% of the vessel passages. The echosounders were downward-facing and highly directional, so their sounds were generally only audible for 2–5 minutes during a vessel passage. In contrast, the non-directional, continuous ultrasonic source (18–26 kHz) was audible 4–6 km from the vessel. High-frequency cetaceans within 1 km of such a vessel are likely to experience temporary hearing threshold shifts, and Southern Resident killer whales have greatly reduced echolocation ranges for 15–20 minutes during the vessel passage. A key recommendation: identify this continuous ultrasonic source and prohibit its use in Canadian waters.
