Binaural Lab: 432 Hz Tones

Binaural Lab plays frequencies as they are.

Nothing is played back from an audio file. The waveform is generated on the spot, which is why the app can show you exactly how many hertz are going to each ear — and why you can tune it to your own hearing, one hertz at a time.

No ads. No subscription. The paid features are a single one-time purchase.

■ Binaural beats The left channel gets "carrier − beat/2" and the right channel gets "carrier + beat/2", as pure tones. You perceive the difference as a beat. Four presets are included: Focus, Relax, Meditation and Deep Sleep. Both channel frequencies are always on screen. Note: each ear has to receive a different tone, so please use headphones or earphones. On speakers the two mix in the air and no beat appears.

■ Single frequencies 432 Hz, 528 Hz, and all nine Solfeggio frequencies (174 / 285 / 396 / 417 / 528 / 639 / 741 / 852 / 963 Hz). The same tone in both ears, so speakers work just as well.

■ Three noise colours White (0 dB/oct), pink (−3 dB/oct) and brown (−6 dB/oct). Continuous sound with no pitch. No headphones needed.

■ Advanced mode (Pro) Set the carrier anywhere from 20 to 1000 Hz and the beat from 0.5 to 40 Hz. • Layer noise over the tone • Left/right balance, for when one ear hears it differently • Choose how long the fade in and fade out take • Isochronic tones — a single tone switched on and off, which works without headphones • Name and save the settings you build

■ Sleep timer 15 to 90 minutes. When the time is up the volume eases down over the fade-out you chose instead of cutting off. It keeps playing with the screen off or while you use other apps, and you can stop it from the Lock Screen and Control Center.

■ Free • Every preset (Focus, Relax, Meditation, Deep Sleep) • 432 Hz and 528 Hz • White, pink and brown noise • Background playback • Sleep timer up to 30 minutes • Up to 3 saved presets

■ Binaural Lab Pro (one-time purchase) • Advanced mode — carrier and beat, freely • All nine Solfeggio frequencies • Isochronic tones • Layer noise over the tone • Left/right balance and fade control • Sleep timer up to 90 minutes • Unlimited saved presets

It is a one-time purchase, so nothing auto-renews and there is nothing to cancel.

■ Before you use it This app is not a medical device and is not intended to diagnose, treat or prevent any illness. No particular effect is guaranteed. If you feel unwell, or have a history of seizures, consult a doctor before use. Avoid long sessions at high volume, and do not use it while driving or anywhere you need to hear what is around you.