Postmasking effects of sensorineural tinnitus: a preliminary investigation.

In this study we provide some preliminary results of our attempt to measure the perception of tinnitus after the termination of a masker. The minimum level to mask tinnitus was determined for a 1-s masker in 10 subjects with sensorineural tinnitus. A continuous masker (parametrically varied in duration, frequency, and level) was then presented to the ear ipsilateral to the tinnitus. At the termination of the masker, subjects were required to press a button when their tinnitus "first returned" and a second button when it returned to "normal loudness." These response times were recorded automatically, and subjects reported what they heard after each trial. At low-level and short-duration maskers, the tinnitus typically was heard immediately after the masker termination. At higher levels and longer durations, different responses were observed. In two subjects, a silent interval was present after the masker, then the tinnitus returned at a softer loudness before returning to its premasker loudness. In one subject, the tinnitus was louder after the masker, and gradually returned to its premasker loudness. In another subject, the tinnitus returned immediately after the masker, but was softer than before. It then gradually increased to its premasker loudness. In the other two subjects, the tinnitus returned immediately to its normal loudness when the masker was terminated at all masker levels and durations. Higher level and longer duration maskers generally produced greater effects. Masker frequency, however, had little effect.