Effects of frequency discrimination training on tinnitus: results from two randomised controlled trials

Abstract

That auditory perceptual training may alleviate tinnitus draws on two observations: (1) tinnitus probably arises from altered activity within the central auditory system following hearing loss and (2) sound-based training can change central auditory activity. Training that provides sound enrichment across hearing loss frequencies has therefore been hypothesised to alleviate tinnitus. We tested this prediction with two randomised trials of frequency discrimination training involving a total of 70 participants with chronic subjective tinnitus. Participants trained on either (1) a pure-tone standard at a frequency within their region of normal hearing, (2) a pure-tone standard within the region of hearing loss or (3) a high-pass harmonic complex tone spanning a region of hearing loss. Analysis of the primary outcome measure revealed an overall reduction in self-reported tinnitus handicap after training that was maintained at a 1-month follow-up assessment, but there were no significant differences between groups. Secondary analyses also report the effects of different domains of tinnitus handicap on the psychoacoustical characteristics of the tinnitus percept (sensation level, bandwidth and pitch) and on duration of training. Our overall findings and conclusions cast doubt on the superiority of a purely acoustic mechanism to underpin tinnitus remediation. Rather, the nonspecific patterns of improvement are more suggestive that auditory perceptual training affects impact on a contributory mechanism such as selective attention or emotional state.

FIG. 1

Training frequencies were defined according to the audiogram. Participants were randomly assigned to train at pure tone frequencies in their region of normal hearing (1 octave below the audiometric edge frequency), in their region of hearing loss (1/4 octave above the edge), or on harmonic sounds that span the region of hearing loss (beginning 1/4 octave above the edge frequency) which have a percept in the region of normal hearing. In this example, if the participant was allocated to one of groups A, D or E, they would train at 2 kHz. If they were allocated to group B, they would train at 5 kHz. If they were allocated to group C, they would train at a harmonic composed of 5, 6, 7 and 8 kHz tones, which would generate a low pitch (∼1 kHz).

FIG. 2

Flowchart of participants per group.

FIG. 3

Hearing thresholds and tinnitus likeness. A Hearing loss (both ears) of all 70 participants are given as light grey, mean threshold is given in black. B Tinnitus likeness spectrographs for all 70 participants are given in grey, mean likeness ratings are given in black. C The graph illustrates a strong association between mean hearing threshold and mean tinnitus likeness of the same frequencies.

FIG. 4

Global and THQ factor scores. Mean THQ scores (±95 % CI) per group at baseline (T0), after 2 weeks training (T1), after 4 weeks training (T2), and at a 1 month follow-up. Broken line cut-off score for bothersome tinnitus. Subsets of questions give THQ factors 1 (emotional component) and factor 2 (effect on hearing) scores. T0 is the second pre-training assessment, which is taken as the stable baseline. T1 is the mid-training assessment, T2 is post-training, and T3 is a 1 month follow-up assessment; n = 14, per group.

FIG. 5

Tinnitus sensation level, bandwidth and dominant pitch. Mean measurements (±95 % CI) of A matched tinnitus sensation level, B tinnitus bandwidth and C dominant tinnitus pitch, in all groups. *p < 0.05, paired t test (corrected for multiple comparisons); n = 14, per group.