Tinnitus Suppression Using AM and FM Acoustic Stimuli

Abstract

Objective 1) Customize amplitude-modulated (AM) and frequency-modulated (FM) acoustic stimuli to suppress tinnitus. 2) Understand the theoretical mechanisms underlying tinnitus suppression. Methods A double-staircase adaptive procedure was utilized to match both the frequency and intensity of the tinnitus. Minimal masking levels for both noise and pure tones were acquired. In a double-blinded procedure, sinusoidally amplitude- and frequency-modulated stimuli were administered. Pre- and post-stimulation tinnitus loudness levels were compared to quantify the effects of suppression and residual inhibition of tinnitus. Multivariate analysis was performed to evaluate independent predictors of tinnitus suppression. Different types and severity of tinnitus and hearing loss were correlated with the effective sounds. Results At present, 18 patients aged 35 to 75 (mean 58.3) with Tinnitus Handicap Index (THI) scores ranging from 12 to 90 (mean 52.6) have been evaluated. Significant associations were found between the duration of the AM and FM stimuli and the effect on tinnitus suppression. 10 out of 18 (56%) patients had a reduction in their tinnitus loudness by 30% or more. Upon comparison with the masking level, reduction in the subjects’ tinnitus was observed when a lower intensity of the modulated stimuli was presented. Subject characteristics that correlated with a significant reduction of the tinnitus will be discussed in detail. Conclusions AM and FM stimuli can decrease the percept of tinnitus significantly. It is postulated that AM and FM stimuli produce synchronized cortical responses to more efficiently compete against tinnitus-induced synchrony.