They can hear sounds ten times fainter than the human ear can even detect. There are four features of the owl's ear that make it so sensitive. They have an extra large ear opening surrounded by deep, soft feathers that funnel sound. Furthermore, the feathers over the ear, auriculars, are modified. Owl auriculars have no barbules, the part of the feather which zip together to make it wind resistant, so the feathers are loose and airy.
Owls also have a moveable flap of skin controlled by muscles around the ear opening.
This flap protects the ear and concentrates sound waves coming from behind. Finally, the owl's entire face acts as an outer ear. The face is two parabolic curves or satellite dishes that funnel sound to the ears. The facial feathers are also compact and tight to aid in the funneling process. Ear tufts do nothing to improve hearing.