The determination of tinnitus loudness considering the effects of recruitment

We have attempted to determine a meaningful measure of tinnitus loudness that considers loudness recruitment. Sixteen subjects with sensorineural tinnitus adjusted the level of a pure tone so that it was (a) at threshold, (b) equal in loudness to the tinnitus, and (c) uncomfortably loud. The pure-tone frequency was (a) at the frequency of the tinnitus pitch, and (b) at the octave frequency between 500 and 4000 Hz having the pure-tone threshold closest to 0 dB HL. In addition, the subjects adjusted the level of a broadband noise so that it (a) was at threshold, (b) just masked the tinnitus, and (c) was uncomfortably loud. These measurements were performed both in the ear ipsilateral and in the ear contralateral to the tinnitus. Formulae based on abnormal loudness functions and uncomfortable loudness levels are presented that convert equal-loudness matches in dB sensation level (SL) into loudness in sones. The level of broadband noise (in dB SL) required to mask tinnitus was about the same in the ipsilateral and in the contralateral ear for most of our subjects, regardless of the ear in which the tinnitus was localized. This noise level (in dB SL) required to mask the tinnitus correlated well with the level (in dB SL) of a tone at the most normal frequency judged equal in loudness to the tinnitus.