Acoustic stimulation treatments against tinnitus could be most effective when tinnitus pitch is within the stimulated frequency range.

Acoustic stimulation with hearing aids or noise devices is frequently used in tinnitus therapy. However, such behind-the-ear devices are limited in their high-frequency output with an upper cut-off frequency of approximately 5-6 kHz. Theoretical modeling suggests that acoustic stimulation treatments with these devices might be most effective when the tinnitus pitch is within the stimulated frequency range. To test this hypothesis, we conducted a pilot study with 15 subjects with chronic tinnitus. Eleven subjects received hearing aids and four subjects noise devices. Perceived tinnitus loudness was measured using a visual analog scale, and tinnitus-related distress was assessed using the Tinnitus Questionnaire. After six months of device usage, reductions of perceived tinnitus loudness were seen only in subjects with a tinnitus pitch of less than 6 kHz. When subjects were grouped by tinnitus pitch, the group of patients with a tinnitus pitch of less than 6 kHz (n = 10 subjects) showed a significant reduction in perceived tinnitus loudness (from 73.4 +/- 6.1 before to 56.4 +/- 7.4 after treatment, p = 0.012), whereas in subjects with a tinnitus pitch of 6 kHz or more (n = 5 subjects) tinnitus loudness was slightly increased after six months of treatment (65.0 +/- 4.7 before and 70.6 +/- 5.9 after treatment), but the increase was not significant (p = 0.063). Likewise, tinnitus-related distress was significantly decreased in the low-pitch group (from 31.6 +/- 4.3 to 20.9 +/- 4.8, p = 0.0059), but not in the group with high-pitched tinnitus (30.2 +/- 3.3 before and 30.0 +/- 5.1 after treatment, p = 1). Overall, reductions in tinnitus-related distress in our study were less pronounced than those reported for more comprehensive treatments. However, the differences we observed between the low- and the high-pitch group show that tinnitus pitch might influence the outcome of acoustic stimulation treatments when devices with a limited frequency range are used.