Isochronic tones, explained

An isochronic tone is a single tone that switches on and off at a steady rate, for example ten times a second. Your ears hear the rhythm as a pulse, and the brain's electrical activity measurably follows a sound that repeats steadily, a response researchers record with EEG. Unlike binaural beats, which need a slightly different tone in each ear to create a beat effect inside your head, an isochronic tone is already pulsing in the sound itself, so it works through regular speakers, not just headphones. Sonor layers a quiet isochronic tone underneath music or ambient sound, at a beat frequency you pick from the bands below. Sonor's pulse fades on and off smoothly rather than clicking.

The five bands

These are the five beat-frequency ranges Sonor groups tones into. The ranges are approximate; different sources draw the lines a little differently. Taller means a faster pulse, not a stronger effect.

What the research says

The clearest finding is simple: the brain's electrical activity measurably follows a sound that pulses at a steady rate (called the auditory steady-state response), and that response is strongest and most reliable near 40 Hz. That's a real, repeatable signal, not proof of a changed state of mind.

Very little research tests isochronic tones directly. A 2026 review of 45 studies found one (source 7). In a 2026 trial of 90 surgery patients, isochronic tones did not change reported anxiety compared with no sound (source 9). Most studies look at the related binaural beat, so treat the isochronic-specific evidence as thinner still. We make no claim about what tones do.

How to use it in Sonor

Keep the tone quiet, under your music. Pick a band by ear and adjust from there. If the pulsing bothers you, turn it off. The pitch of the tone is a separate choice: carrier frequencies.

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.

Sources

1. Picton TW, John MS, Dimitrijevic A, Purcell D. Human auditory steady-state responses. Int J Audiol 2003;42(4):177-219.
   The brain's response follows a sound that pulses at a steady rate, strongest near 40 Hz; this is a measured response, not proof of a changed state of mind.
2. Becher AK et al. Intracranial EEG power and phase synchronization changes during monaural and binaural beat stimulation. Eur J Neurosci 2015.
   Recordings inside the brain showed the clearest response to 40 Hz pulsing (monaural) beats.
3. Ingendoh RM, Posny ES, Heine A. Binaural beats to entrain the brain? (systematic review). PLoS ONE 2023;18(5):e0286023.
   Of 14 EEG studies of binaural beats, those that played the beat inside pink noise found no following.
4. Chaieb L, Wilpert EC, Reber TP, Fell J. Auditory beat stimulation and its effects on cognition and mood states. Front Psychiatry 2015;6:70.
   A review of auditory beat stimulation that calls it a possibly promising tool and sets out to explain why findings are often contradictory.
5. Huang TL, Charyton C. A comprehensive review of the psychological effects of brainwave entrainment. Altern Ther Health Med 2008;14(5):38-50.
   A 2008 review of 20 studies of rhythmic light and sound stimulation. It mixed light and sound, and predates most of the controlled EEG work.
6. Kanzler SA, Cidral-Filho FJ, Prediger RD. Effects of binaural beats and isochronic tones on brain wave modulation: literature review. Rev Mex Neurocienc 2021;22(6).
   Only 2 of 17 trials reviewed used isochronic tones, so isochronic-specific evidence is thin.
7. Papadatou L, Pastiadis K, Papadelis G, Kimiskidis VK. Amplitude modulated audio signals in brainwave entrainment: effects on psychophysiological functions, a scoping review. Auditory Perception & Cognition 2026;9(2):125-152.
   Of 45 peer-reviewed studies from 2010 to 2024, only one tested isochronic tones.
8. Galambos R, Makeig S, Talmachoff PJ. A 40-Hz auditory potential recorded from the human scalp. Proc Natl Acad Sci U S A 1981;78(4):2643-2647.
   The first recording of a 40 Hz response from the human scalp.
9. Akkurt O, Ekici Ö. Effect of binaural beats and isochronic tones on anxiety during impacted mandibular third molar surgery: a randomized controlled trial. Int J Oral Maxillofac Surg 2026.
   Ninety patients, 30 each with binaural beats, isochronic tones or no sound. Anxiety questionnaires did not differ between groups.