The ear is mainly divided into the outer and middle ear and the inner ear. The ear is the one with the function of sound transmission and the balance of the division. The outer ear is made up of the outer auricle and the external auditory canal outside. The external auricle is a cartilaginous structure, and the outer 1/3 of the external canal is cartilage, and the inner 2/3 is bone structure. The length of the external auditory canal is about 3.6 cm. Deep in the external auditory canal is an oblique membranous structure called the tympanic membrane. Within the tympanic membrane is the middle ear cavity, which includes the tympanic chamber, tympanic membrane, eustachian tube, and the contents of the tympanic cavity such as the auditory tuberosity. The inner ear includes the cochlea, the semicircular canal, and other structures, and is the main organ for sound transmission, as well as the body’s balance function.