Freebase Dali

That's called diffusion. You can see examples of this in acoustic treatments in recording studios. The basic idea is to create odd angles, depths and distances... and the incoming sounds are reflected off these angles in such an uneven and inconsistent way, the reflection is broken up. Diffused. There is no noticeable return echo or flutter.

The ideal design for an ear would be more close to the design of a cat ear, where there would be a funneling surface to guide sound down into the ear. Diffusive formations could help break the sound up a little, but this is useful after the sound has been focused on it, like in a cat's ear.
Our ears have diffusive properties that serve no purpose because there isn't an effective enough cone to make it useful.

Reflecting sound away from our ears does nothing for our hearing except impede it.