UI researcher Albert Feng made the discovery while studying the concave-eared torrent frog.

Feng says the frogs live in a very noisy ambience at Huangshan Hot Springs, west of Shanghai.

It’s by a creek that goes from trickling to a roaring stream that sounds like a waterfall when there is a torrential rain or thunderstorm, he told the Chicago Sun-Times, noting the noise forced him and his colleagues to shout at each other to communicate. The frogs cope by going ultrasonic.

That explained what had been a mystery to scientists: why the frogs have concave ears: thin eardrums are needed to pick up ultrasound and concave ears shorten the path to the eardrum, enabling ultrasound transmission.

The newspaper said the discovery might lead to improvements in hearing aids, as did earlier research on the frogs.

The study is reported in this month’s issue of Nature magazine.