Magnitude estimation and the "paradoxical" loudness of tinnitus.

Ten patients with sensorineural hearing loss and tinnitus matched external tones to the tinnitus pitch. These matches were followed by magnitude estimates to measure the loudness function of tones at 1 kHz at the presumed tinnitus frequency (i.e., at the average frequency matching the pitch of the tinnitus), magnitude estimates of the tinnitus itself, and loudness matches of external tones to the tinnitus. The slope of the loudness function at 1 kHz is substantially smaller than the slope at the presumed tinnitus frequency. Most importantly, the magnitude estimates of the tinnitus coupled with intensity matches to the tinnitus provide coordinates that typically lie near the loudness function of the external tone used in the intensity match. Because the slope of the loudness function is much greater at the tinnitus frequency than at 1 kHz, the magnitude estimate of tinnitus loudness corresponds to a lower sensation level at that frequency than at 1 kHz. This finding favors the conclusion that rapid changes in loudness of external tones at the tinnitus frequency account for the "paradoxical" loudness of the tinnitus. The conclusion is independent of any mathematical description of the loudness function.