What frequency is used for deep sleep?
Which Hz should I pick for sleep?
Sleep-oriented binaural audio almost always sits in the delta range, roughly 0.5 to 4 Hz. Lucid's sleep sessions centre on 3.5 Hz for that reason. But the number is less meaningful on its own than most apps imply, and it is worth understanding what it refers to.
What the number refers to
When a track is labelled 3.5 Hz, that is the difference between the two carrier tones, not the pitch you hear. Two carriers around 200 Hz that are 3.5 Hz apart produce a 3.5 Hz difference. The audible pitch is the carrier; the 3.5 Hz is the beat between them.
The bands, and where they came from
These ranges are borrowed from EEG research, where they describe patterns of electrical activity recorded from the scalp during different states. The names are descriptive categories, not settings.
| Band | Range | Associated with |
|---|---|---|
| Delta | 0.5–4 Hz | Deep, slow-wave sleep |
| Theta | 4–8 Hz | Drowsiness, early sleep, deep meditation |
| Alpha | 8–14 Hz | Relaxed wakefulness, eyes closed |
| Beta | 14–30 Hz | Active, alert thinking |
| Gamma | 30–100 Hz | Concentrated attention, still debated |
The reasoning behind sleep audio is that presenting a delta-range beat may encourage activity in a similar range. That proposed mechanism is called entrainment, and it is the part of the field where the evidence is genuinely mixed.
What the evidence supports
Studies on binaural beats and sleep exist, and some report improvements in self-reported sleep quality or time to fall asleep. Most are small, use different frequencies, durations and protocols, and often lack blinding — difficult to do well when participants can hear the intervention. Reviews tend to conclude that effects are plausible but inconsistent, and that the field needs larger and better-controlled work.
So the frequency is a reasonable, research-informed starting point rather than a dial that produces a guaranteed state. Treat 3.5 Hz as a sensible default for sleep, not as a dose.
What matters more than the number
- Duration: a session that ends after five minutes is unlikely to help you fall asleep. Longer sessions, or ones that run while the screen is locked, fit the actual situation better.
- Volume: quiet enough to ignore. Sleep audio you keep noticing is working against you.
- Ambience: rain or brown noise masks the sounds that actually wake people — traffic, a partner, a building.
- Consistency: the same routine at the same time is doing more work than any specific frequency.