Post-9/11 quiet calmed marine mammals
Stress hormones in North Atlantic right whales fell during a lull in shipping activity following the September 11, 2001 attacks on the World Trade Center and Pentagon. The finding suggests that ship noise may do more than annoy the marine mammals.
Observations in the wild have already shown that noisy ships can change whale behavior. Engines and propellers give off low-frequency sounds that carry well underwater and overlap with the frequencies whales use to chitchat. To be heard in a din, the social animals increase the volume, pitch or length of their calls. Often they turn away from sudden sounds or avoid loud waters altogether.