According to the second national sample survey of people with disabilities, there are 27.8 million people with hearing disabilities in China, the highest number among the five major disabilities, and 20,000 to 30,000 newborns with severe congenital hearing impairment are born every year. Deafness has become one of the most common chronic diseases in modern society and should be given our full attention. Deafness can be classified as organic deafness, functional deafness and pseudo-deafness according to the nature of the lesion, and organic deafness can be classified as conductive deafness, sensorineural deafness and mixed deafness according to the location of the lesion. Conductive deafness: Conductive deafness can be caused by any structural or functional disorder in the outer ear, middle ear or inner ear sound conduction pathway. In conductive deafness, the air-conduction hearing loss generally does not exceed 60 dB, while the bone conduction hearing is basically in the normal range. Sensorineural deafness: The impairment of sound sensation or nerve impulse transmission due to damage to the hair cells of Corti, auditory nerve, auditory transmission pathway or hearing centers at all levels is called sensorineural deafness, and both air and bone conduction hearing is reduced. In this case, the damage to the hair cells caused by noise, infection, ototoxic drugs and genetic factors is called sensorineural deafness (cochlear deafness), which often has the phenomenon of resonance. If the lesion is located in the auditory nerve and its conduction pathway, it is called neurological deafness and central deafness (collectively called retrocochlear deafness), such as auditory neuroma and auditory neuropathy, etc. The speech recognition rate is often significantly decreased, and the patient complains that he/she can hear the sound but cannot distinguish its meaning. Mixed deafness: If the patient has both conductive deafness and sensorineural deafness caused by lesions in the outer ear and/or middle ear, as well as lesions in the hair cells of the Corti apparatus or the auditory nerve, the patient is considered to have mixed deafness. The World Health Organization (WHO) in 1997 classified hearing loss into the following grades according to the average threshold of air conduction at 500Hz, 1000Hz, 2000Hz and 4000Hz: mild hearing loss (26~40dBHL), moderate hearing loss (41~55dBHL), moderate to severe hearing loss (56~70dBHL), and severe hearing loss (71~90dBHL). (71~90dBHL), and very severe hearing loss (≥91dBHL). Common methods for assessing the cause and location of deafness 1.Pure tone hearing threshold test (directional condition response test) Pure tone hearing threshold test responds to the hearing sensitivity of the subject ear to pure tones of various frequencies and estimates the degree of auditory damage. The general pure-tone hearing threshold test is suitable for adults, children over 12 years of age, and children over 6 months of age for directional conditioned reflex testing (visual reinforcement audiometry or conditioned play audiometry) 2. Acoustic conductance test Acoustic conductance test is an objective test of the middle ear conduction system, inner ear function, auditory nerve, and brainstem auditory pathway function, and is suitable for all types of people. Generally speaking, the curve is type A for anyone with normal middle ear function; type As is common when the middle ear conduction system activity is limited such as ear cherry, fixed auditory chain or obvious thickening of the tympanic membrane; if its activity is increased, such as interruption of the auditory chain, atrophy of the tympanic membrane, healing perforation and abnormal opening of the eustachian tube, the curve can be Ad; type B curve is mostly seen in those with fluid in the tympanic chamber and obvious adhesions in the middle ear; type C curve indicates eustachian tube C curve indicates dysfunction of the eustachian tube and negative pressure in the tympanic chamber. 3.Auditory brainstem response audiometry (ABR) is divided into auditory brainstem response threshold and auditory brainstem response latency, ABR refers to the detection of brainstem bioelectric response induced by acoustic stimulation, ABR can be used to determine high frequency hearing threshold, neonatal and infant hearing screening, identification of organic and functional deafness, diagnosis of small horn occupational lesions in the brain, etc. 4.Distortion otoacoustic emission (DPOAE) is an objective auditory function test that depends on the integrity of the overall cochlear function and is closely related to the function of the outer hair cells of the cochlea. 5. 40 Hz auditory correlation potential is an auditory steady-state evoked potential, which is a type of mid-latency response. It is mainly used for objective assessment of hearing threshold thresholds, and is especially valuable for determining hearing thresholds at frequencies below 1000 Hz. It can help to understand the low frequency of newborn hearing screening and ABR response in those who are not elicited. 6.Steady-state auditory evoked potential (ASSR) is an EEG response evoked by a continuous or steady-state sound stimulus signal. ASSR is an objective listening method that can detect various frequency thresholds and is important in the audiometry of people who cannot perform behavioral audiometry or whose behavioral audiometry does not yield satisfactory results (especially infants and children ≤ 6 months of age). 7. Speech recognition rate refers to the percentage of words that the subject ear is able to understand in the measured vocabulary. Combined with audiological assessment it can be used to determine the type of deafness at first glance. 8. Newborn hearing screening: Newborns receive auditory brainstem response or otoacoustic emission screening within 6 to 48 hours after birth, and if they do not pass the screening within one month, the diagnosis is confirmed within three months and intervention is performed before 6 months of age.