The temporal course of the masking of tinnitus as a basis for inferring its origin.

For patients with tinnitus and sensorineural hearing loss, the intensity of broad-band noise required to mask the tinnitus increases by as much as 45 dB during a 30-minute period if the patient is exposed to noise. In contrast, the intensity required to mask an external tone remains nearly constant. Some speculations which might account for this result are offered. Excess neural activity is posited to be the physiological determinant of tinnitus and to be central, generated in the brainstem postsynaptic to the eighth nerve.