A randomised controlled trial published in June in Sleep, the journal of the Sleep Research Society, adds useful evidence to a question a lot of people quietly wonder about: do sleep sound apps actually work?
The short answer: on their own, not meaningfully.
What the researchers did
Vazzaz and colleagues at the University of Sussex, working with wellbeing platform Unmind, ran a randomised controlled trial with 495 working adults who reported disturbed sleep. Mean age 32.7. 55.8% female.
4 groups, 4 weeks. App-based Bedtime Stories, Sleep Sounds, Sleep Skills, or a digital control.
The target was sleep disturbance: a general measure of how disrupted or poor someone's sleep is, based on their own reported experience. Measured with validated questionnaires before and after.
What they found
Every group improved, including the control. None of the 3 audio interventions beat the control on sleep disturbance. For Sleep Sounds specifically, the effect size was small and not significant (Hedges' g = 0.14, 95% CI −0.11 to 0.39). Same flat pattern across sleep-related impairment, mental health, wellbeing, and pre-sleep arousal.
The authors were direct about it: these audio tools are safe and well-tolerated, but their use "as standalone treatments for sleep disturbance is not supported by these findings."
This study looked at one specific thing: generic, undifferentiated audio content delivered through an app, the kind of soundscapes and stories now bundled into most wellbeing platforms. The library included white and pink noise tracks, so those sit inside the result. It says nothing about sound therapy in general or about audio engineered specifically for sleep. For white noise machines on their own, see do white noise machines actually help you sleep?
Why this matters to how we think about sound and sleep
At Cambridge Sleep Sciences, there's a difference we've always cared about: playing sounds at a sleeper, versus engineering sound to work with the sleeping brain. Most sleep audio does the first. Pleasant, relaxing, passive. SleepEngine™ does the second. Barely audible and working passively while you sleep, the soundwaves guide your brain through the sequence of healthy sleep cycles. Using sound to get to sleep is not new, and it has a long history behind it. What is new is engineering it around sleep physiology and then measuring what happens.
SleepEngine™ has been through a second study of its own: twenty adults whose insomnia had lasted six months or more and hadn't responded to conventional treatment, in a 12-week pilot study run by an NHS family doctor. One week of baseline, twelve weeks of nightly use, then eight weeks with no device at all. After twelve weeks, more than two thirds saw a clinically meaningful improvement in sleep quality (n=19), measured on the Pittsburgh Sleep Quality Index, the industry standard measure of sleep quality. At week 20, the improvement in sleep quality still held eight weeks after participants stopped using the device. By then, 84% had a clinically meaningful improvement, and more than half were sleeping well, up from 1 in 19 at the start (n=19). Presented at World Sleep Congress 2025 and now in peer review for publication: read the write-up. Generic sounds and engineered soundwaves are different interventions, and different results should be expected.
So, do sleep sound apps work?
If you've tried a sleep-sound app and found it pleasant but not transformative, you're not alone. The limitation may sit in the approach rather than in you. Sound can do more than soothe. The question is whether it's been engineered to.
If you're weighing up what to try instead, we set out sleep earbuds, headbands and wearable-free options side by side.
Read more about SleepEngine™ →
Source: Vazzaz J, Matcham F, Economides M, Bolton H, Cavanagh K. USleep: Efficacy of App-Based Audio Interventions to Improve Sleep Disturbance in Working Adults, a Multi-Arm Randomised Controlled Trial. Sleep, 2026; 49(9): zsag154. doi:10.1093/sleep/zsag154. Trial registration ISRCTN13426045.
