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Whales and some other marine mammals likely hear sonar signals more than we previously thought, according to a new study. 

Commercially available sonar systems are designed  to create signals beyond the range of hearing of such animals. However, they also emit signals that are known to be within their hearing range, scientists found.

The sound is likely very soft and audible only when the animals are within a few hundred meters of the source, said authors of the study. 

The signals would not cause any actual tissue damage, but it's possible that they affect the behavior of some marine mammals, which rely heavily on sound to communicate, navigate, and find food, the release added.

"These signals are quiet, but they are audible to the animals, and they would be relatively novel since marine mammals don't encounter many sounds in this range," said Southall, who is the former director of the Ocean Acoustics Program of the National Oceanic and Atmospheric Administration, in the press release.

"These sounds have the potential to affect animal behavior, even though the main frequency is above what they primarily hear. It may be that environmental assessments should include the effects of these systems. This may not be a major issue, but it deserves further exploration," added Southall.

Authors added that for marine mammals the it might sound like one continuous, high-pitched hum or ping.

"If you think of a keyboard on a piano, the ships would be hitting the low notes quite hard, the middle keys would be most of the sounds of the animals themselves, and the sonar systems we studied would be relatively quieter sounds in the top few octaves on the right of the keyboard," added Southall in the press release.

The findings are published in the journal PLOS ONE.