Figure 4.

Intensity discrimination. a, Intensity discrimination threshold as a function of frequency at 30 dB SL for 10 control subjects (solid black squares) and 16 tinnitus subjects (open blue triangles). Error bars show ±1 SD of the mean. The average threshold for tinnitus-matched stimuli (the solid red circle with error bars) was the arithmetic mean from 14 tinnitus subjects, including 9 young (small open red circles) and 5 old (small solid red circles). The asterisk and the line below represent a significant difference between the groups. b, The same as a except at 70 dB SL. There was no significant difference in intensity discrimination at tinnitus-matched frequencies between the young and old tinnitus subjects at either 30 dB SL (p = 0.10) or 70 dB SL (two-tailed, two-sample t test, p = 0.61).