(1) Conductive deafness: Common causes include cerumen blocking the ear canal, otitis media, otosclerosis, and interruption of the auditory chain so that sound cannot be transmitted effectively. Damaged area: outer or middle ear. Treatment: Generally, the symptoms can be cured or reduced by medication or surgery, otherwise hearing aids can be used with mostly good results. (2) Sensorineural deafness: The common causes include excessive noise, hereditary deafness, natural aging, consumption of ototoxic drugs, auditory neuroma and the sequelae of radiotherapy for nasopharyngeal carcinoma, etc., which prevent information from being transmitted to the brain completely and accurately. Therefore, people with sensorineural deafness often have the following manifestations. (1) Reduced ability to distinguish speech: Hearers cannot hear certain speech sounds, so they often cannot understand what other people are saying. (ii) Reduced hearing range: Deaf people cannot hear smaller sounds, but because the volume they perceive increases particularly quickly, their highest comfortable volume differs greatly from that of people with normal hearing. (③Decreased temporal processing ability: When loud and small sounds occur over a short period of time, deaf people have less difficulty than normal people in detecting small sounds, and speech is mixed with loud and small sounds, so they have difficulty understanding speech in a hurry or in noise. ④ Reduced audio selection ability: Good audio selection ability can help listeners distinguish speech and filter noise in a noisy environment, while deaf people generally have poor audio selection ability, so they have difficulty talking in noise and understanding what is being said. Damaged area: Inner ear or cochlear nerve. Treatment: If there is a problem with the nervous system, immediate medical attention should be sought; if deafness persists after treatment or due to damage to the inner ear, hearing aids should be fitted, and in severe cases, electronic cochlear implants may be considered. (3) Mixed deafness: Etiology consists of a combination of conductive and sensorineural deafness symptoms or congenital dysphasia of the outer ear, middle ear, inner ear and auditory system. Site of impairment: inner ear or auditory nerve plus outer or middle ear. Treatment: Medication and quality hearing aids. Short-term conductive deafness usually does not have long-term effects on hearing after medical treatment, but damage to the inner ear is permanent and the function of the auditory system to process sound is impaired.