Echolocating bats generate ultrasound via the larynx and emit the sound through the open mouth or, much more rarely, the nose.The latter is most pronounced in the horseshoe bats ("Rhinolophus spp."). Bat echolocation calls range in frequency from 14,000 to well over 100,000 Hz, mostly beyond the range of the human ear (typical human hearing range is considered to be from 20 Hz to 20,000 Hz). Bats may estimate the elevation of targets by interpreting the interference patterns caused by the echoes reflecting from the tragus, a flap of skin in the external ear.