Clinically, hearing impairment is divided into two categories: conductive hearing loss and neurological (sensory) hearing loss. Conductive hearing loss refers to hearing loss caused by damage to the "tympanic membrane-ossicular chain" system from the external auditory canal to the middle ear; neurological hearing loss belongs to sensorineural lesions, which refers to damage to the nerve conduction pathway from the cochlea or auditory nerve in the inner ear to the auditory center, resulting in hearing loss or disappearance, also known as sensorineural hearing loss. In the former, sound waves can also be transmitted to the inner ear through bone conduction from the skull to cause sensation, while in the latter, hearing is weakened or lost due to nerve damage. Tinnitus is the conscious hearing of a sound in the ear, which is an irritating lesion of the cochlear nerve trunk or nerve endings. Currently, most scholars also advocate that it should be classified as a hearing impairment.