Measures of tinnitus: step size, matches to imagined tones, and masking patterns

Measures of the pitch (0.2% step) and loudness (2 dB step) of tinnitus were obtained using a forced-choice double-staircase procedure. In the first experiment, for seven subjects with tinnitus, the difference limen of pitch and loudness matches made to tinnitus within a single block of trials was not significantly different from that of the same measurements made to comparable external stimuli. In the second experiment, subjects matched the pitch of real and imagined tones. For 3 of 7 subjects with tinnitus and for 2 of 14 normal-hearing subjects, the difference limens were nearly equal. In the first experiment, therefore, three of the subjects with tinnitus might have matched to an imagined tone and not to their tinnitus. In the third experiment, thresholds of tones near the presumed tinnitus frequency were measured. Thresholds were approximately equal in the presence of the tinnitus. However, in the presence of a masking tone at the presumed tinnitus frequency and level, thresholds were unequal. Thus, tinnitus did not behave as a tonal masker.