The science · Brain waves
Delta, explained
Delta is the slowest of the five EEG bands, below about 4 Hz. Clinical EEG guidelines associate it with deep, non-REM sleep. Here is what researchers have measured with sound pulsed at delta rates, and what Sonor does with the band.
What the research says
The clinical EEG glossary defines the delta band as 0.1 to under 4 Hz, and describes deep non-REM sleep as dominated by slow delta waves of 0.5 to 2 Hz (Kane et al. 2017).
Steady-state brain responses can be recorded for sounds repeated at rates from 1 to 200 Hz, but they are most prominent near 40 Hz in waking listeners, not at delta rates (Picton et al. 2003).
A 2023 systematic review of 14 EEG studies of binaural beats found delta-range beats tested in 3 of them. None of the 14 reported an increase in delta power. The authors judged the studies too different to pool (Ingendoh et al. 2023).
A 2024 study of 12 healthy adults compared afternoon naps with no sound against binaural beats at 0, 0.25 or 1 Hz. Time to deeper sleep was shorter with 0.25 Hz beats than with no sound. The researchers did not detect the brain following the beat. The study was funded by KYOCERA Corporation, and a patent application was filed on the results. 0.25 Hz is below Sonor's delta range (Fan et al. 2024).
A 2026 study of 20 healthy students compared one night of delta-range binaural beats with two nights without intervention. It had no night with a sham sound, so the beat cannot be separated from sound in general (Dabiri et al. 2026).
Separate research uses short sounds timed to a sleeper's own slow brain rhythm. That method reads the sleeper's EEG in real time. Sonor does not do this, so those results do not apply to Sonor's continuous pulse.
Overall, the evidence that delta-rate sound changes delta activity or any listener outcome is weak. We make no claim about what delta tones do for you.
How Sonor uses it
Sonor's delta range pulses the tone from 0.5 up to, but not including, 4 times a second. The picker offers 1, 2 and 3 Hz. The pulse plays continuously, quietly under music or ambient sound. It is not timed to your own brain waves.
This isn't medical advice. Pulsing audio can affect people with epilepsy or a seizure disorder, so check with a doctor before using it if that applies to you.