The normal hearing value of the ear is between (-10) and (+10) dB, and any hearing within this range is considered normal hearing, if the hearing loss is below +25 dB, mild deafness should be considered. Deafness is considered by the general public as inability to hear, but in clinical practice hearing loss is also called deafness. There are two types of deafness: air conduction hearing loss and bone conduction hearing loss. If the hearing loss is purely air conduction and normal bone conduction, it is considered to be conductive hearing loss, while if the bone conduction and air conduction are the same, it is considered to be neurological hearing loss, which requires further clinical examination and, if necessary, brainstem evoked potential examination or CT examination of the middle ear.