The Outer Ear-

Two functions of the human ear are Hearing and Balance. The auditory system senses sound, while the vestibular system manages balance. Adult ear canals range from about 2.3cm to 2.9cm, averaging 2.54cm. Most resonate between 1500 and 4000Hz, with an average frequency of 2700Hz and a gain of 16dB. The vagus nerve (cranial nerve X) is located at the bottom of the ear canal, where touching it can trigger Arnold’s reflex, an automatic cough. The tympanic membrane measures about 9mm high and 8mm wide, held in place by the annular ring, creating a watertight and airtight seal between the external and middle ear. Acoustic energy causes the TM to vibrate in response to sound. The ear canal features two bends: the first is near the aperture, and the second follows shortly after.