Investigation of tinnitus induced by sound and its relationship to ongoing tinnitus

Tinnitus was temporarily induced by monaurally presented sound, and its level monitored using a dichotic loudness-matching task. The first experiment found no effect of varying the level, bandwidth, or center frequency of an inducing noise on the level or duration of the induced tinnitus; nor was there any difference when tones or different noises were used to induce tinnitus. The rated loudness of the tinnitus, however, increased with the level and decreased with the center frequency of the noise. The second experiment investigated tinnitus induced by a 1-kHz, 95-dB SPL tone in 53 subjects with thresholds in the normal range, but with varying degrees of ongoing tinnitus that ranged from no discernible sound sensation at all, through an apparently normal but usually inaudible noise or ringing, to constant or near-constant tinnitus. Individual differences in induced tinnitus were found that were related to differences in ongoing tinnitus; for example, the levels of induced and ongoing tinnitus were positively correlated. The results suggest that some kinds of ongoing tinnitus may arise from the auditory process responsible for induced tinnitus.