Abstract: This review included eight studies (with a total of 590 participants). Seven studies investigated the effects of hearing aids, four combination hearing aids and three sound generators. Seven studies were parallel-group RCTs and one had a cross-over design. In general, risk of bias was unclear due to lack of detail about sequence generation and allocation concealment. There was also little or no use of blinding. No data for our outcomes were available for any of our three main comparisons (comparing hearing aids, sound generators and combination devices with a waiting list control group, placebo or education/information only). Data for our additional comparisons (comparing these devices with each other) were also few, with limited potential for data pooling. Hearing aid only versus sound generator device only One study compared patients fitted with sound generators versus those fitted with hearing aids and found no difference between them in their effects on our primary outcome, tinnitus symptom severity measured with the Tinnitus Handicap Inventory (THI) at 3, 6 or 12 months (low-quality evidence). The use of both types of device was associated with a clinically significant reduction in tinnitus symptom severity. Combination hearing aid versus hearing aid only Three studies compared combination hearing aids with hearing aids and measured tinnitus symptom severity using the THI or Tinnitus Functional Index. When we pooled the data we found no difference between them (standardised mean difference -0.15, 95% confidence interval -0.52 to 0.22; three studies; 114 participants) (low-quality evidence). The use of both types of device was again associated with a clinically significant reduction in tinnitus symptom severity. Adverse effects were not assessed in any of the included studies. None of the studies measured the secondary outcomes of depressive symptoms or depression, anxiety symptoms or generalised anxiety, or health-related quality of life as measured by a validated instrument, nor the newly developed core outcomes tinnitus intrusiveness, ability to ignore, concentration, quality of sleep and sense of control. There is no evidence to support the superiority of sound therapy for tinnitus over waiting list control, placebo or education/information with no device. There is insufficient evidence to support the superiority or inferiority of any of the sound therapy options (hearing aid, sound generator or combination hearing aid) over each other. The quality of evidence for the reported outcomes, assessed using GRADE, was low. Using a combination device, hearing aid or sound generator might result in little or no difference in tinnitus symptom severity. Future research into the effectiveness of sound therapy in patients with tinnitus should use rigorous methodology. Randomisation and blinding should be of the highest quality, given the subjective nature of tinnitus and the strong likelihood of a placebo response. The CONSORT statement should be used in the design and reporting of future studies. We also recommend the use of validated, patient-centred outcome measures for research in the field of tinnitus.

Plain-language summary: Our review identified eight randomised controlled trials with 590 participants in total. Seven studies looked at the effects of hearing aids, four combination hearing aids and three sound generators. Seven studies allocated participants into parallel groups and in one study participants tried each intervention in a random order. The outcomes that we looked for were severity of tinnitus symptoms, depression, anxiety, quality of life and side effects. In general, the risk of bias in the studies was unclear. There was also little or no use of blinding. We did not find any data for our outcomes for any of our three main comparisons (comparing hearing aids, sound generators and combination devices with a waiting list control group, placebo or education/information only). There were also few data for our additional comparisons (comparing these devices with each other) and it was difficult to pool (combine) the data. One study compared patients fitted with sound generators with those fitted with hearing aids and found no difference between them in their effects on our primary outcome, tinnitus symptom severity, at 3, 6 or 12 months. The use of both types of device was associated with a clinically significant reduction in tinnitus symptom severity. Three studies compared combination hearing aids/sound generators with hearing aids alone and measured tinnitus symptom severity. When we combined the data for tinnitus symptom severity we found no difference between them. The use of both types of device was again associated with a clinically significant reduction in tinnitus symptom severity. Adverse effects were not assessed in any of the included studies. None of the studies measured depressive symptoms or depression, anxiety symptoms or generalised anxiety, or other important outcomes of interest in this review. Where outcomes that we were interested in for this review were reported, we assessed the quality of the evidence available as low. Using a hearing aid, sound generator or combination device might result in little or no difference in tinnitus symptom severity.