Binaural beats, an auditory illusion created by the brain, may increase the amount of deep sleep, the most restorative phase of sleep.

noli's read

The concept is based on the idea that the brain synchronizes its electrical waves with the frequency difference between two sounds perceived separately by each ear. Scientific research on this subject is currently mixed. Some small-scale studies (often observational evidence or preliminary RCTs) do suggest potential effects on relaxation or perceived sleep quality. However, as a meta-analysis published in 'Journal of Sleep Research' points out, the overall evidence lacks consistency and the size of the observed effects is often modest. It is therefore difficult to conclude that there is universal clinical efficacy. What is stated holds true for the principle of the auditory illusion, but the extrapolation regarding a significant and reliable increase in deep sleep remains, at this stage, a hypothesis awaiting more robust evidence.

the sources

No named source held this one up — that absence is part of the verdict.