Deafness is a hearing dysfunction that can be classified by degree as mild, moderate, severe, or profound deafness. It can be divided into conductive deafness, sensorineural deafness and mixed deafness according to the part of the lesion. The main causes of conductive deafness are: acute and chronic otitis media, otitis externa and cerumen embolism, secretory otitis media, tympanic membrane perforation and congenital external auditory atresia. The main causes of sensorineural deafness are: noise damage, Méminaire’s disease (Meniere’s syndrome), ototoxic drugs, sudden deafness, familial deafness, age-related deafness, and head trauma. Mixed deafness has both conductive and sensorineural hearing impairment factors. Hearing loss classification of deafness: mild hearing loss: 26 to 40 decibels; moderate hearing loss: 41 to 55 decibels; moderate to severe hearing loss: 56 to 70 decibels; severe hearing loss: 71 to 90 decibels; very severe hearing loss: greater than 91 decibels.