Continuous active sonar may not address noise pollution of killer whale habitats

A new type of sonar called continuous active sonar is believed to mitigate some of the more serious acoustic impacts associated with traditional sonar, such as marine mammal strandings and hearing loss. Although continuously active sonar is typically quieter, its continuous nature can interfere with killer whale communication in the wild.

Branstetter et al. tested the effects of continuously active sonar along with other sources of marine noise on a pair of killer whales to determine their effects.

“Killer whales use sound to communicate across distances when visibility is limited,” said author Brian Branstetter. “Their calls can identify individuals, which group they belong to, where they are and which direction they are traveling. Too much noise can impair these abilities.”

The researchers tested the effects of continuous active sonar, amplitude modulated noise and Gaussian noise on two killer whales. The whales were trained to force air through their blowhole as if they were blowing a raspberry when they perceived a sound that the researchers could hear and see as blowing.

While the whales could use an off-frequency listening strategy to detect some signals, the functions of continuous active sonar overlapped too much with their demands for effective communication.

The authors hope the research will inspire other teams to study the effects of noise pollution on killer whale behavior, while also exploring other solutions to filter out the noise.

“Our team is currently studying the perception of very short sounds in the presence of masking noise,” said Branstetter. “We are also interested in how broadband calls from killer whales can be used to improve signal detection in noisy environments.”

Source: “Acoustic masking of tonal and species-specific signals by continuous active sonar, amplitude-modulated noise, and Gaussian noise in killer whales (Orcinus orca)”, by Brian K. Branstetter, Michael Felice, Todd Robeck, Marla M. Holt and E. Elizabeth Henderson, magazine of Acoustic Society of America (2024). The article is available at .