A Mixed-Methods Trial of Broad Band Noise and Nature Sounds for Tinnitus Therapy: Group and Individual Responses Modeled under the Adaptation Level Theory of Tinnitus.

Mithila Durai,Grant D Searchfield

doi:10.3389/fnagi.2017.00044

Mithila Durai, Grant D Searchfield

Open Access

https://doi.org/10.3389/fnagi.2017.00044

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Abstract

Objectives: A randomized cross-over trial in 18 participants tested the hypothesis that nature sounds, with unpredictable temporal characteristics and high valence would yield greater improvement in tinnitus than constant, emotionally neutral broadband noise.Study Design: The primary outcome measure was the Tinnitus Functional Index (TFI). Secondary measures were: loudness and annoyance ratings, loudness level matches, minimum masking levels, positive and negative emotionality, attention reaction and discrimination time, anxiety, depression and stress. Each sound was administered using MP3 players with earbuds for 8 continuous weeks, with a 3 week wash-out period before crossing over to the other treatment sound. Measurements were undertaken for each arm at sound fitting, 4 and 8 weeks after administration. Qualitative interviews were conducted at each of these appointments.Results: From a baseline TFI score of 41.3, sound therapy resulted in TFI scores at 8 weeks of 35.6; broadband noise resulted in significantly greater reduction (8.2 points) after 8 weeks of sound therapy use than nature sounds (3.2 points). The positive effect of sound on tinnitus was supported by secondary outcome measures of tinnitus, emotion, attention, and psychological state, but not interviews. Tinnitus loudness level match was higher for BBN at 8 weeks; while there was little change in loudness level matches for nature sounds. There was no change in minimum masking levels following sound therapy administration. Self-reported preference for one sound over another did not correlate with changes in tinnitus.Conclusions: Modeled under an adaptation level theory framework of tinnitus perception, the results indicate that the introduction of broadband noise shifts internal adaptation level weighting away from the tinnitus signal, reducing tinnitus magnitude. Nature sounds may modify the affective components of tinnitus via a secondary, residual pathway, but this appears to be less important for sound effectiveness. The different rates of adaptation to broadband noise and nature sound by the auditory system may explain the different tinnitus loudness level matches. In addition to group effects there also appears to be a great deal of individual variation. A sound therapy framework based on adaptation level theory is proposed that accounts for individual variation in preference and response to sound.Clinical Trial Registration: www.anzctr.org.au, identifier #12616000742471.

Highlights

Subjective tinnitus is the involuntary perception of one or more sounds by an individual, in the absence of an external physical source (Henry et al, 2005; Moller, 2006; Kaltenbach, 2011; De Ridder et al, 2014)
The average baseline outcome measures of participants at the start of the trial is provided in Table 2
This effect was largely due to broadband noise (BBN) sound therapy which resulted in a 8.2 point reduction of Tinnitus Functional Index (TFI) scores (Meikle et al, 2012); this was significantly different to the 3.2 point reduction following 8 weeks of Nature sound administration

Summary

Introduction

Subjective tinnitus is the involuntary perception of one or more sounds by an individual, in the absence of an external physical source (Henry et al, 2005; Moller, 2006; Kaltenbach, 2011; De Ridder et al, 2014). It is broadly understood to arise as a result of peripheral lesions in the auditory system resulting in altered cortical input. This triggers compensatory neuroplasticity changes across several overlapping brain networks (Schecklmann et al, 2013a,b; Vanneste et al, 2011, 2013; Husain and Schmidt, 2014). Final tinnitus magnitude is thought to result from differences in personality and activity within auditory, emotion, attention, and memory networks (Searchfield et al, 2012; Searchfield, 2014; Durai et al, 2015). A failure to account for the heterogeneous nature of tinnitus has likely contributed to the difficulties in identifying useful therapies

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