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Noise Headlines and Top Story- Updated January 16, 2018

WHO Sees Correlation Between Noise Levels and Annoyance
- National Cooperative Highway Research Program Seeks Potential Synthesis Study Topics
- NOAA: Ship Noise Reduces Range of Fish Vocalizations 
- Wind Turbine Syndrome Deemed a Myth
- Transportation Research Board Showcases Latest Studies
- Birds Stressed By Constant Noise from Oil and Gas Operations
- Interior Department Proposes to Open Offshore Leasing
- Australia to Deploy Continental Acoustic Sensor Network
- Consumer Product Safety Commission Rejects Exemption for Noisy Toys
- Highway and Aviation Noise Exposure Linked to Obesity
- University of Toronto Warns Transit Impulse Noise Could Damage Hearing



Vancouver’s Voluntary Slow-Down Reduced Ship Noise up to 9.4 dB
A two-month experiment in which piloted commercial ships transiting Haro Strait, east of Vancouver Island, British Columbia, voluntarily slowed to 11 knots resulted in measurable reductions in underwater noise. The Port of Vancouver sponsored the research to assess the potential benefits of reducing vessel-generated underwater noise in Haro Strait to improve foraging among endangered orcas, also known as killer whales.

“Haro Strait is known to be a key foraging area for the endangered Southern Resident Killer Whale (SRKW) in the summer months. [It] is also a geographically constrained area with a busy shipping lane, and was identified through other research to be a hotspot for potential loss of foraging by SRKW as a result of vessel noise,” according to the Port’s report of preliminary findings.

The experiment was initiated by the Port’s Enhancing Cetacean Habitat and Observation (ECHO) Program, which identified it as a priority measure to gain a better understanding of the relationship be-tween vessel speed and noise, along with the potential benefit to foraging by killer whales. It sought to answer these main questions:

• How does reduced speed change the under-water noise generated by a specific vessel and by class of vessels? 

• How does reduced speed change the total underwater ambient noise received at a specific location of importance to the killer whales?

• What are the predicted resultant effects on killer whale behavior and foraging, given the changes in noise?

More than 60 percent of the vessels transiting Haro Strait during the trial last summer voluntarily slowed their speed to 11 knots. The actual reduction in speed depended on an individual vessel’s normal cruising speed. The measured speed reductions and resulting decreases in noise, by class of vessel, are as follows:

• bulk/general cargo ships, 2.2 knot reduction in speed and 4.9 dB reduction in source sound level;

• container ships: 6.9 knot reduction in speed and 9.4 dB reduction in source sound level;

• passenger ships: 6.2 knot reduction in speed and 8.1 dB reduction in source sound level;

• vehicle carriers: 5.8 knot reduction in speed and 9.3 dB reduction in source sound level.

Researchers recorded a total of 33 matched pairs of accurate vessel source level measurements for the same vessel at two stations. “When the vessel source level and vessel speed data relationships for all 33 vessels are plotted on one chart, analysis of the trend line predicts that slowing speed by 40 percent reduces broadband monopole noise emissions by approximately 10 dB,” the report concludes. “This relationship is even stronger above 15 kHz, the echolocation frequency range for killer whales.” 

While deemed successful in lowering vessel speed to reduce underwater noise levels in a critical habitat area, the study was not able to document the effect on orcas because sightings of the mammals were down 70 percent from the previous year. Researchers speculate that “the poor return of Chinook salmon stocks observed this season is thought to be a significant factor in the reduced inshore presence of SRKW.”

These results are preliminary, with more details to come. The question remains whether the trade-off between lower sound levels and longer passage times associated with slower speeds is beneficial to the whales. 

 Copyright 2018 Great Circle Communications LLC
No unauthorized posting, forwarding, or any other form of transmission of this material, by any means, in whole or in part, is allowed.  
 
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