1. Conductive deafness: (1) blockage of the external ear canal; (2) tympanic membrane perforation (due to trauma or otitis media); (3) repeated inflammation of the middle ear, causing destruction or interruption of the auditory chain and adhesion fixation; (4) congenital malformation of the auditory chain (2) congenital deafness: (1) congenital heredity, there are more than 70 known hereditary diseases related to congenital deafness; (2) maternal infection during pregnancy, especially viral infection; (3) maternal application of drugs toxic to the ear due to certain diseases during pregnancy or inappropriate medication after birth of infants and children, which is one of the main causes of congenital deafness at present.