Notched Sound Therapy: A Primer

Among audiologists, the use of newer sound therapies for tinnitus can be a controversial topic. For decades, the use of Tinnitus Retraining Therapy has been shown to be a moderately successfully approach for inducing the habituation response in tinnitus sufferers.¹ Newer sound therapies, however, purport to directly lower the volume of a patient’s tinnitus tone.² Researchers have hypothesized that sustained listening to specific sound therapies results in neuroplastic changes in the brain that can reduce tinnitus tone volume.² In general, however, research in this space has been limited by small sample sizes and a lack of high quality randomized controlled trials.⁵

Notched Sound Therapy is a treatment for tinnitus that was originally developed by European academics. It involves a three step process. In the first step, users match their tinnitus frequency (various techniques can be used for this, including a manual tinnitus frequency slider as well as the 2-Alternative Forced Choice search method typically used by audiologists).³ In the second step, a software program processes audio (either music or white noise) by removing a frequency band centred at the user’s tinnitus frequency.⁴ This process is called “notching.” In the third and final step, users listen to Notched Sound Therapy with headphones.⁴ Over the span of weeks to months, their tinnitus volume can be decreased.⁴ Over the course of a therapeutic listening program spanning several months, a user’s tinnitus frequency may shift.³ Because this may result in a “notch” that does not overlay their tinnitus frequency, it’s necessary for users to periodically re-check their tinnitus frequency, creating new Notched Sound Therapy as needed.³

The theory underlying the “notching” process is that the activity of the auditory neurons that underlie the tinnitus percept can be suppressed through neuroplastic changes in the brain.⁴ Researchers theorized that the strengthening of lateral inhibitory connections between “normal” auditory neurons and “abnormal” auditory neurons (responsible for tinnitus) could result in a reduction in tinnitus tone volume.²

In 2009, Italian researchers recruited 43 people for an experiment with Notched White Noise, a type of Notched Sound Therapy created by “notching” white noise.³ Participants listened daily for 12 months.³ Of those who received the experimental treatment, 4 of 20 reported that their tinnitus tones had been eliminated entirely.³ In the experimental arm, the average tinnitus volume reduction reported was approximately 75%.³

Subsequently, German researchers recruited 16 participants for a similar trial with Notched Music.² Participants listened to sound therapy for 2 hours daily for 12 months.² The average volume reduction in the treatment arm was approximately 26%.²

Following the promising results of small experiments with small sample sizes, the same German research group recruited 100 participants for a clinical trial of Notched Music Therapy (Notched Sound Therapy produced with music).⁷ Participants listened for 3 months daily.⁷ The reduction in tinnitus volume was observed to be small, but was still present 1 month after the cessation of therapy.⁷ This study was published in 2016.

The aforementioned clinical trial also recorded reported harms in the placebo and treatment groups. The placebo group of tinnitus sufferers listened to regular music, and the treatment group listened to notched music. There was no statistically significant difference between harms reported in the treatment and placebo groups, suggesting that the risks of Notched Music in tinnitus sufferers is equivalent to the risks of listening to music in general.⁷ The most commonly reported harms were: a consistently louder tinnitus tone (10.9%), the perception of an additional tinnitus tone (8.7%), and an increased awareness of the tinnitus tone (6.5%).⁷

Currently, it's too early to draw definitive conclusions from the existing preliminary research.⁵ An independent analysis of the experimental results in the sound therapy space concluding the following:

"Overall there is currently insufficient evidence to support or refute the routine use of individual sound therapy options. It is likely, however, that sound therapy combined with education and counseling is generally helpful to patients." ⁵

A critical review of the Notched Sound Therapy literature similarly concluded that there isn’t currently enough evidence to support the usage of this therapy for standard use (with one important caveat: this review was written prior to the Notched Music clinical trial that was later conducted in Germany).⁶ Feedback from the reviewer suggested that there was too much heterogeneity in experimental protocols and designs to accurately survey its efficacy (for example, variations in the “notching” algorithm used).⁶ Additional work remains to be done to determine the optimum patient profile for the usage of Notched Sound Therapy.⁶

In summary, Notched Sound Therapy is a type of sound therapy that is created removing a frequency band centred at the user’s tinnitus frequency (“notching”).⁴ It’s hypothesized to induce neuroplastic changes in the brain that reduce the hyperactivity of auditory cortical neurons responsible for the tinnitus percept.⁴ Early research has been promising but limited by methodological limitations such as small sample sizes.⁵ A larger clinical trial has subsequently been performed but generated only a small reduction in tinnitus tone volume.⁷ Currently, it’s too early to draw a definitive conclusion about its efficacy either way, but is available for individuals seeking to try it.⁵

References:

1. Kim B.J., Chung S.W., Jung J.Y., Suh M.W. (2014). Effect of different sounds on the treatment outcome of tinnitus retraining therapy. Clin Exp Otorhinolarygol 2:87-93
2. Okamoto H., Stracke H., Stoll W., Pantev C. (2010) Listening to tailor-made notched music reduces tinnitus loudness and tinnitus-related auditory cortex activity. Proc Natl Acad Sci U S A 107: 1207-1210.
3. Lugli M, Romani R, Ponzi S, Bacciu S, Parmigiani S (2009) The windowed sound therapy: a new empirical approach for an effective personalized treatment of tinnitus. Int Tinnitus J 15:51-61.
4. Teismann, H., Okamoto, H., Pantev, C. (2011). Short and intense tailor-made notched music training against tinnitus: The tinnitus frequency matters. Plos ONE, 6, 1-8.
5. Hoare, DJ, Searchfield, GD, El Refaie A, Henry JA. (2014). Sound therapy for tinnitus management: practicable options. J Am Acad Audiol. 25:62-75
6. Bennett, M. (2012). Critical Review: Efficacy of notched-sound therapy for neural plasticity mediated tinnitus treatment. Unpublished (Master’s Thesis)
7. Pantev et al. (2016). Clinical trial on tonal tinnitus with tailor-made notched music training. 16:38

DISCLAIMER AND DECLARATION OF CONFLICT OF INTEREST:

This article was written by Dr. Peter Phua, M.D., and is not intended as professional medical advice. It is provided solely for general informational purposes only. 

About the Author

Dr. Peter Phua, M.D. is the CEO of AudioNotch, a software company that allows users to create their own customized Notched Sound Therapy.