Transcript:

An Earful of Bats

ambience: bat echolocation signals
The sound of an echolocating bat. Scientists don't fully understand the workings of the bats sophisticated sonar system. It may have something to do with the shape of the bat's ears. I'm Jim Metzner and this is the Pulse of the Planet.

Mueller: The ears of bats are really special structures.

Mechanical Engineer Rolf Mueller

Mueller: Basic parts are the same as the ears that you and I carry on our heads, but if you look at the shape of these structures, it's very different. An example would be the tragus, the little knob that you have at the frontal part of your ear. In bats the tragus is often really, really large, like a big mushroom that is standing in front of the ear.

We have made artificial bat ears from rubber, and then we have put something like a tragus in front of those. Then, we have listened to the sound from the recordings. The other thing that we have done is computer simulation that you have a digital model of the shape of an ear with or without tragus, and what we found in those studies is that the tragus makes the behavior of the ear more complicated. So, you get a more complicated pattern in how the ear reacts to sound coming in from different directions. But every time the bat is listening, it changes the shape of its ears. Bats are real athletes when it comes to their ear. A bat - in about one-tenth of a second, a bat can change the shape of its ear. So that's a whole new level of complexities a whole new dimension to this whole process of sonar operation that we don't have, as human listeners, and that our technical sonar systems also don't have.

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