Some observations on the masking and post-masking effects of tinnitus

The symptom of tinnitus is likely shared by several underlying pathologies. It is funda-mental to the investigation and treatment of tinnitus to be able to reliably quantify different types of tinnitus. In one experi-ment we required patients to increase the level of a broadband noise until it just masked their tinnitus. Regardless of where in the head they perceive their tinnitus, in most patients the minimum level (in sound pressure level or sensation level) required to mask the tinnitus is similar in both ears. In a few other patients, the tinnitus cannot be masked or requires high levels in the contra-lateral ear. We have found this masking procedure valuable in measuring tinnitus following the administration of tocainide. In some patients the tocainide seemed to reduce the magnitude of the tinnitus (required lower masker levels to mask the tinnitus) whereas in others there was some evidence that the tinnitus got worse (higher masker levels were required). In another experiment, we quantified tinnitus percep-tion following the termination of a masker. Several different patterns were evident. After the termination of the masker, the tinnitus either (a) returned to normal immediately, (b) returned immediately but was at a softer loudness, (c) was absent for a time before gradually returning to normal, (d) was absent for a time before abruptly returning to normal, or (e) was louder than normal before gradually returning to normal. Increasing masker duration and masker level prolonged the effects.