How well can marine mammals filter out noise?

Anyone who has struggled to make out a conversation in a loud bar or restaurant has experienced auditory masking — a phenomenon in which the presence of one sound makes it harder to hear another. Understanding the toll of auditory masking on pinnipeds — seals, sea lions, and walruses — is important for underwater conservation.

Jones et al. explored the hearing abilities of these animals, working with two seals, one sea lion, and one walrus, to test their ability to perceive sounds through noise.

A key variable in evaluating the effect of auditory masking is the critical bandwidth — the range of frequencies over which noise can affect a signal at a specific tone.

“Critical bandwidths tell us how specialized that portion of the cochlea is for a specific range of frequencies,” said author Ryan Jones. “The narrower your critical bandwidth is, the better you are at extracting a signal from noise in that frequency band.”

By conducting tests on trained animals, the researchers probed the critical bandwidths of multiple pinniped species at frequencies ranging from 100 to 10000 Hertz. While all species exhibited smaller critical bandwidths at lower frequencies, looking at critical bandwidth as a proportion of center frequency tells a different story. The walrus and sea lion subjects saw increasing critical bandwidth ratios at lower frequencies, while the seals showed a more constant critical bandwidth ratio at all frequencies.

This suggests that seals are better adapted to hear low-frequency sounds through noise, but the authors caution that it’s not that simple.

“It’s a double-edged sword. Yes, they’re able to adapt well and extract signals from noisy environments better than perhaps walruses or sea lions,” said Jones. “The downside is they are more sensitive in general at lower frequencies, and they tend to be using that acoustic space more readily.”

The researchers plan to explore this by determining the loudness thresholds at which noise can start to interfere with pinniped hearing.

Source: “Critical bandwidth measurements in pinnipeds,” by Ryan A. Jones, Jillian M. Sills, Ann E. Bowles, Seri Aldana, Noah Packard, and Colleen Reichmuth, Journal of the Acoustical Society of America (2026). The article can be accessed at https://doi.org/10.1121/10.0044870 .