Sleep brainwaves: delta, theta and alpha
| Brainwave | Frequency | When it shows up |
|---|---|---|
| Delta | 0.5–4 Hz | Deep, slow-wave sleep |
| Theta | 4–8 Hz | Drowsiness and light sleep |
| Alpha | 8–12 Hz | Relaxed and awake, eyes closed |
Binaural beats aim to match these slow rhythms. SleepHz uses 2 Hz for Deep Sleep and 6 Hz for Drift Off.
How binaural beats work
A binaural beat plays a slightly different tone in each ear. SleepHz plays 180 Hz on the left and 182 Hz on the right, and your brain perceives the 2 Hz difference as a slow pulse.
That only works with headphones, because each ear has to hear its own tone. Research on binaural beats for sleep is small and mixed, so treat them as a relaxation aid.
Brown noise vs white noise
White noise has equal energy at every frequency, so it sounds bright, like static. Brown noise puts more energy into low frequencies, so it sounds deep and soft, like steady rain or a distant waterfall.
If you need to cover traffic, voices or a snoring partner, brown noise is usually the easier sound to sleep with.
Ocean waves and rainforest rain
Nature sounds work like brown noise with a gentle rhythm. Ocean Waves rises and falls in slow swells, so it pairs well with slow breathing: in as a wave builds, out as it recedes.
Rainforest Rain layers steady rain with a few soft, distant birds. Both are generated live in your browser, so they loop seamlessly all night with no repeating audio file.
A simple SleepHz bedtime routine
- Put on soft headphones for Deep Sleep or Drift Off, or use a speaker for Ocean Waves, Rainforest Rain or Sleep Noise.
- Set the volume low, just above what you can hear.
- Choose Auto-stop: 1 hour to fall asleep, or up to 8 hours to sleep through.
- Press play, dim the screen and breathe slowly.