The research team wired up a false killer whale with sensors to record brain activity and conducted a series of sound experiments.
Having taught the whale that a bleeping sound preceded a loud noise, they found that it began to lower its hearing response – reflected by smaller brain waves - when the bleep was made, in anticipation of the loud noise to follow.
The scientists think that cetaceans which use sonar for navigation and object detection may have evolved the ability to alter hearing levels in order to protect themselves from their own, very loud, emitted noises.
Team leader Dr Paul Nachtigall, of the University of Hawaii, told BBC Nature: "The sounds they produce are very loud; they can be over 230-decibel pulses.” The creatures then need to be able to hear “very quiet echoes".
A whale’s ability to alter its responses to incoming sound would not necessarily protect it from sudden, unexpected loud noises emitted by man-made systems, which are thought to cause harm to their echo-locating systems.
These include naval sonar and commercial seismic survey operations.
Some sort of recognisable warning would be required in order for a whale to anticipate a loud event and lower its response level before it occurred.
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