Continuous active sonar may not fix noise pollution of killer whale habitats
Continuous active sonar may not fix noise pollution of killer whale habitats lead image
An emerging type of sonar, called continuous active sonar, is thought to mitigate some of the more severe acoustic impacts associated with traditional sonar, such as marine mammal strandings and hearing loss. Although continuous active sonar is typically quieter, its continuous nature may interfere with the communication of killer whales in the wild.
Branstetter et al. tested the effects of continuous 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 distance when vision is limited,” said author Brian Branstetter. “Their calls can identify individuals, which group they belong to, their location, and which direction they are traveling. Too much noise can interfere with these capabilities.”
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, like blowing a raspberry, when they detected a noise, which could be heard and seen as bubbles by the researchers.
While the whales could use an off-frequency listening strategy to detect some signals, the features of the continuous active sonar overlapped too much with their calls for effective communication.
The authors hope that the research will inspire other teams to study the effects of noise pollution on killer whale behavior while they study other solutions to filtering out the noise.
“Right now, our team is investigating the perception of very short duration sounds in the presence of masking noise,” Branstetter said. “We are also interested in how killer whale broadband calls may be used to enhance signal detection in noisy environment.”
Source: “Auditory masking of tonal and conspecific 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, Journal of the Acoustical Society of America (2024). The article can be accessed at https://doi.org/10.1121/10.0028626 .
