The site of deafness can occur at any part of the auditory system. There are four types of deafness depending on the site of the lesion. If the lesion occurs in the outer ear, it is called conductive deafness, and if the lesion occurs in the inner ear or in the auditory nerve fibers, it is called sensorineural deafness. If both of these lesions are present, it is called mixed deafness. If the lesion is located in the auditory center, it is called central deafness. Conductive deafness is a condition in which the sound energy in the inner ear is reduced due to the obstruction of the outer ear canal and middle ear lesions, resulting in varying degrees of hearing loss. Conductive deafness can occur in the external auditory canal, middle ear cavity, eardrum, auditory bone, and eustachian tube. Common causes of conductive deafness include atresia of the external auditory canal (microtia), interruption of the auditory chain, otitis media, otosclerosis, tympanic membrane perforation, and ear canal cerumen. Hearing loss due to conductive deafness is mostly mild to moderate. All frequencies may be affected, or only low frequency loss. Audiograms often show a mild or moderate decrease in air conduction, while bone conduction thresholds are within the normal range. Common conductive deafness can be treated with hearing aids and surgery, or the latest middle ear implant technology, vibrating sound bridges, can be chosen for hearing reconstruction. Deafness can occur at any part of the auditory system. There are four types of deafness, depending on the location of the lesion. If the lesion occurs in the outer ear, it is called conductive deafness, and if the lesion occurs in the inner ear or in the auditory nerve fibers, it is called sensorineural deafness. If both of these lesions are present, it is called mixed deafness. If the lesion is located in the auditory center, it is called central deafness. Conductive deafness is a condition in which the sound energy in the inner ear is reduced due to the obstruction of the outer ear canal and middle ear lesions, resulting in varying degrees of hearing loss. Conductive deafness can occur in the external auditory canal, middle ear cavity, eardrum, auditory bone, and eustachian tube. Common causes of conductive deafness include atresia of the external auditory canal (microtia), interruption of the auditory chain, otitis media, otosclerosis, tympanic membrane perforation, and ear canal cerumen. Hearing loss due to conductive deafness is mostly mild to moderate. All frequencies may be affected, or only low frequency loss. Audiograms often show a mild or moderate decrease in air conduction, while bone conduction thresholds are within the normal range. Common conductive deafness can be treated with hearing aids and surgery, or the latest middle ear implant technology, vibrating sound bridges, can be chosen for hearing reconstruction. Sensorineural deafness is deafness caused by lesions in the sensory cells of the cochlea and/or the auditory nerve fibers of the eighth pair of cranial nerves. Most common forms of sensorineural deafness are seen in acoustic injury, congenital deafness, age-related deafness, hereditary or genetic deafness, and Meniere’s disease. When the sensorineural mechanisms are damaged for various reasons, the function of converting mechanical energy into electrical energy is correspondingly diminished. Some of the subsequent auditory mechanisms may also change. Among them, the following are the most common: l. Weakening of the sound-sensing function of the cochlear receptor cells 2. Weakening of the frequency discrimination function of the cochlea 3. Reduction of the dynamic range of hearing One of the consequences of sensorineural deafness is the phenomenon of loudness resonance, i.e., abnormal loudness. Compared to the normal ear, patients with sensorineural deafness can perceive smaller suprathreshold intensities as loud sounds. This clock phenomenon leads to a significant reduction in the patient’s dynamic range (the difference between threshold and discomfort threshold). The reduced dynamic range and reduced frequency discrimination can affect speech perception. In most cases, this effect on speech perception can be predicted from their audiogram. Compared to equivalent degrees of conductive deafness, speech perception is poorer in patients with sensorineural deafness due to the aforementioned effects. The utility of the patient’s residual hearing is greatly reduced by the effects of diminished spectral processing and reduced dynamic range. On the audiogram, sensorineural deafness often shows parallel decreases in air and bone conduction thresholds. The difference between air and bone conduction does not exceed 10 dB. Solutions for sensorineural deafness include medications, surgery, middle ear implantation – vibrating sound bridge if the deafness is between moderate and severe, or cochlear implantation if the deafness is severe or even very severe. Mixed deafness: The presence of simultaneous lesions in both sound-transmitting and sound-sensing structures. Examples include long-term chronic suppurative otitis media, advanced otosclerosis, and blast deafness. Mixed deafness can be treated with hearing aids or hearing reconstruction surgery, or if the hearing loss is in the moderate to severe range, middle ear implants – vibrating sound bridges – are also an option. Central deafness – rare, hearing center lesions in the brain, often combined with other disorders. Currently, only auditory brainstem implantation can treat central deafness. This procedure is not currently performed in China due to the high requirements of the procedure.