Ear-flaps concentrate sound waves: mammals
The external ear-flaps of many mammals aid hearing by concentrating sound waves.
"It is only among mammals that ears become noticeable, even striking, because of the visible external ear-flaps behind the narrow opening of the outer ear tube…The most obvious use of the ear-flap, though not necessarily the most important, is to gather and concentrate sound waves." (Foy and Oxford Scientific Films 1982:167)
Learn more about this functional adaptation.