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Constant noise or sound in the head may be due to ringing in the ears which is called tinnitus. An individual perceives this in the absence of any outside sounds. It happens in various ENT disorders like exposure to a loud sound like a gun shot, and resolves without any treatment in most cases within hours. Tinnitus can also be due to sensorineural hearing loss and is also common. In these cases tinnitus is the symptom of an underlying hearing problem. From the history of your mother, it appears to be more related to an ENT problem.
All cases of tinnitus, especially those associated with hearing problems should be thoroughly investigated by an ENT specialist. Sometimes, tinnitus is one-sided due to problems in one ear.
Examination is performed to exclude hearing problems, ENT problems, problems related to the carotid artery and the jugular vein in addition to the temporomandibular joint. TMJ problems can cause noise within the head but this is not continuous.
Your mother's symptom of noise requires a thorough ENT examination before any other examination is contemplated. Please take the opinion of an otorhinolaryngologist. Thank you.