Floppy, folded, small, large—dogs’ ears come in many shapes, but they all serve the same purpose: as funnels for sound. Even during the quiet hours of the night, the world is a noisy place for dogs, who can hear the high-frequency pulse of the crystal resonator used in digital alarm clocks and bodily vibrations of termites in the walls. Domestic dogs can hear significantly higher frequency sounds than humans, although not as high as cats.

University of Cincinnati researcher Pete Scheifele, also the director of UC’s Bioacoustics and Canine Audiology Clinic, is developing a hearing aid that will help dogs with acquired hearing loss. Erect ears facing forward indicate that she’s engaged, and slightly pulled-back ears signal that she’s feeling friendly; ears laid tightly back against the head suggest a fearful or timid reaction. This makes examination challenging and predisposes dogs to a variety of ear ailments, including parasites and yeast infections.

To give additional dog knowledge to your Dog 101, here are some interesting facts about our favorite four-legged friends.

How to train my dog not to jump Get a dog