Grading and classification of deafness 1.Grading of deafness: According to WHO 1980 deafness grading standard, the average speech frequency pure tone hearing threshold is divided into 5 grades. 1) Mild deafness: Hearing threshold of pure tones and speech by audiometer is 26-40dB. 2) Moderate deafness: Hearing threshold of 41-55dB. 3) Moderate and severe deafness: Hearing threshold of 56-70dB. 4) Severe deafness: Hearing threshold of 71-91dB. 5) Total deafness: Hearing threshold of pure tones exceeds 91dB. 2. Classification of deafness: It can be divided into three categories according to the site and nature of lesion. (1) Conductive deafness: Deafness caused by lesions in the outer ear and middle ear, and the transmission of sound waves to the inner ear, such as cerumen embolism and otitis media. (2) Sensorineural deafness: A lesion of the cochlear spiral apparatus that cannot change sound waves into neural excitation or a disorder of the nerve and its central pathway that cannot transmit neural excitation; or a lesion of the central cerebral cortex that cannot distinguish speech, collectively called sensorineural deafness. (3) Mixed deafness: the presence of lesions in both the transmitter and sensorineural bodies.