The Om frequency: 136.1 Hz, where the number comes from, what it is and is not known to do

The number is not ancient. It is a calculation the Swiss mathematician and musicologist Hans Cousto worked out in 1978 and set out in his book The Cosmic Octave (Die kosmische Oktave in the original German). Cousto’s idea was simple: take any astronomical period, express it as a frequency, and double it until it lands in the range the ear can hear. Doubling a frequency raises it by one octave, so the result is “the same note” many octaves up — the same way the C on a piano is the same note as the C three octaves above it.

For the Earth’s year he used the length of the tropical year, 31,556,925.9747 seconds (a little over 365.2422 days) — the figure that defined the second itself between 1956 and 1967, when it was set at 1/31,556,925.9747 of the tropical year for 1900. One cycle every 31.5 million seconds is a frequency of about 0.0000000317 hertz. Double it 32 times and it reaches the low end of a man’s singing voice:

You can do that on a phone calculator. Nothing in it is mystical, and nothing in it is wrong: it is an exact conversion of one period into one pitch. What it does not do is explain why 32 octaves rather than 31 or 33. Thirty-one gives 68 Hz and thirty-three gives 272 Hz, both just as much “the year” as 136.1 is. Thirty-two was chosen because it lands in a comfortable register for a voice or a string. The pitch is a convention, chosen by a person, from a number that is itself a human definition of a day. That is worth holding onto when the tone is later described as something the planet “emits”.

A second thing follows from the arithmetic. On the modern concert standard, where A above middle C is 440 Hz, the nearest note to 136.1 Hz is C♯ below middle C, at 138.59 Hz. The Om frequency sits about 31 cents below it — a third of a semitone flat, less than a quarter-tone, which is why some guides call it “a slightly flat C sharp”. If you instead tune so that C♯ is exactly 136.1 Hz, the A above middle C lands at 432.1 Hz. That is where the familiar 432 Hz tuning claim and the Om frequency meet: they are the same tuning described from two different notes, and the 432 versus 440 comparison covers what listening tests have and have not found about it. The Earth-year tone is not evidence for 432; it is the same arithmetic wearing a different label.

Cousto paired his Earth-year tone with Indian classical music, and that pairing is the whole basis of the name. He wrote that the drone instruments of Indian music — the tanpura, and the sitar tuned against it — were traditionally pitched close to this frequency, with the tonic (sa) at or near 136 Hz, and that this was also the pitch at which Om is chanted. From that observation the tone acquired its names: the Om frequency, the Sa, the Earth tone, the year tone.

We cannot verify the historical part of that, and we would not want you to take it on our word. Indian classical music has no single fixed reference pitch; the tonic is set by the lead performer’s voice or instrument and varies by singer, by instrument and by era. Tanpuras are tuned to many pitches. A tradition that chose its tonic by the singer may well have landed near 136 Hz for a low male voice, since C♯ below middle C sits comfortably in that range — but “often near” is a different claim from “traditionally set to the Earth’s year”, and the second claim starts with Cousto, not with any older source we can find.

The rest grew up around the tone as it was taken up by sound-healing practice in the 1980s and after. In the tuning-fork trade, 136.1 Hz forks are sold as “Om forks” and described as grounding, centring or calming, and are often assigned to the heart chakra in the Western chakra-colour systems of that period, where each centre is paired with a planet or a note. Those pairings vary from one vendor to the next, which is a reasonable sign that they were assigned rather than discovered. In chanting practice, Om is sung at whatever pitch the voice falls on; the idea that it has one correct frequency belongs to the fork catalogues, not to the Upanishads.

None of this makes the tone useless, and the practices around it are old and meaningful to a great many people. It means only that the page has to keep two columns separate: what the tradition says, which is this section, and what has been measured, which is the next. The 528 Hz page on this site draws the same line for the Solfeggio tones; the Om frequency deserves no less and no more.

The imaging and EEG work is small and mostly uncontrolled. The most-cited paper, Kalyani and colleagues (International Journal of Yoga, 2011), put twelve healthy volunteers in an fMRI scanner and compared audible Om chanting with saying “ssss” and with rest. Chanting was associated with reduced activity in limbic regions — orbitofrontal cortex, anterior cingulate, parahippocampal gyri, thalami, hippocampi and the right amygdala — and the authors suggested, as a hypothesis, that vibration of the ear might be stimulating the vagus nerve. It is a pilot with twelve people and no clinical outcome. Harne and Hiwale (Applied Psychophysiology and Biofeedback, 2018) recorded EEG in 23 novices before and after thirty minutes of loud chanting and reported higher theta power afterwards, averaged across the scalp, with no specific band otherwise singled out. Saini and colleagues (Annals of Neurosciences, 2024) used high-density EEG in twenty young men and found that five minutes of chanting and five minutes of listening to chanting changed activity in broadly similar cortical areas — which is the nearest the literature comes to testing listening rather than doing, and it still used a recording of a voice, not a tone. Zhang, Peng and Chen (Frontiers in Psychology, 2022) had 33 students rate unpleasant images while chanting and found the images rated as less unpleasant, with event-related potential changes to neutral images.

The heart-rate-variability studies point at the breath, not the pitch. Inbaraj and colleagues (International Journal of Yoga, 2022) measured HRV in nineteen yoga practitioners and seventeen novices before and after five minutes of loud chanting and found the high-frequency component rose more in the experienced group. Hotho and colleagues (Frontiers in Physiology, 2022) is the most mechanistically interesting: nine trained speech practitioners chanted Om at roughly three breaths per minute, and heart period, blood pressure and respiration became strongly synchronised, with an unexpected 0.1 Hz oscillation appearing in heart rate and blood pressure. That is the signature of slow breathing, the same one studied under the name resonance breathing, and nothing in the paper depends on the pitch of the voice. The humming literature summarised on the humming resonance page reaches the same conclusion from the other direction.

The clinical trials bundle Om with other things. Two randomised trials in hypertensive patients from the same Kerala group, Anjana and colleagues (Journal of Ayurveda and Integrative Medicine, 2022) and Rajagopalan and colleagues (Journal of Basic and Clinical Physiology and Pharmacology, 2023), reported lower blood pressure, better sleep scores and better HRV after two months — of Om chanting combined with yoga nidra, against usual care with no attention control. Whatever helped, the design cannot say which part. The one trial of listening rather than chanting, Bhoot and colleagues (Annals of Neurosciences, 2025), gave sixty stage-1 hypertensive patients a daily recording of Om chanting “composed at 528 Hz” for a month and reported lower pulse and blood pressure and higher HRV than usual care. Note the frequency: 528, not 136.1. If that trial is evidence for anything, it is evidence for a chant recording at a different pitch, with no sham audio to compare against.

The one review says what reviews of small literatures say. Mooventhan and colleagues (Advances in Mind-Body Medicine, 2025) screened 130 papers and included 21, concluded that chanting appears safe and feasible with effects on autonomic and cardiovascular measures, and called for larger and better-controlled studies. It is a narrative review, not a meta-analysis, and it does not mention 136.1 Hz because none of its 21 papers do.

So the honest summary is this. Chanting Om is a slow-breathing practice with some small, mostly positive, mostly uncontrolled physiology behind it, and the plausible mechanism is the breathing. Listening to a chant recording has two studies, one of them at 528 Hz. Listening to a 136.1 Hz sine tone has none. If you want the measured thing, chant or hum; the tone is at most a reference pitch for doing so.

Nothing that has been measured. A pure tone at 136.1 Hz is a single sine wave, the simplest sound there is: one frequency, no harmonics, no rhythm. It is not a binaural beat, so there is nothing for the auditory brainstem to extract and nothing that could entrain a brain rhythm — brainwave bands run from about 1 to 100 Hz, and a 136 Hz pressure wave in the air is not a 136 Hz signal in the cortex any more than a 440 Hz tuning fork is. The pages on how binaural beats work and on brainwave frequencies explain the difference properly; the short version is that a carrier pitch is the note you hear, and a beat frequency is the slow pulse the brain can follow. This page has a carrier and no beat.

What a sustained low tone is good for is the thing drones have always been good for: a steady reference that gives attention somewhere to rest and the breath something to pace against. Many people find a low, unchanging sound easier to sit with than silence, which fills with whatever is in the room and in the head. That is a use, not an effect, and it does not depend on the number being 136.1. The same drone at 130 or 140 Hz would do the same job. If 136.1 means something to you because of the tradition behind it, that meaning is yours to keep; we only ask that you do not mistake it for physiology.

Two practical notes. First, headphones are not needed — the tone is identical in both ears, so a speaker is fine and more comfortable for a long sit. Second, a sine wave is tiring at volume in a way music is not, because it never pauses; set it just loud enough to hear clearly over the room and no louder, and stop if your ears feel full or ring afterwards. The safety page applies here as much as it does to beats.

If you want a beat on top of the tone, the main generator will put a 6 Hz theta beat on a 136 Hz carrier. It works in whole hertz, so it rounds the carrier to 136; the difference of a tenth of a hertz is below anything a listener can tell apart, but this page exists partly so that the exact figure is available to anyone who wants it. The meditation page explains what that theta preset is for and what the evidence for it looks like, and the pure tone generator plays any single frequency from 60 to 1000 Hz if you want to compare 136.1 against its neighbours.

The useful way to use a fixed pitch is to hum against it. This turns the tone from something you consume into a reference you tune to, which is closer to how a tanpura is actually used: the drone is sounded so the singer has something to sing against.

1. Start the tone and find it in your voice. Hum with the mouth closed and slide the pitch up or down until the beating between your voice and the speaker disappears and the two sounds seem to lock. C♯ below middle C sits comfortably in most male voices; it is low for many female voices, and the honest fix is to hum an octave higher, at 272.2 Hz, which is still “the same note” by Cousto’s own octave logic.
2. Let the exhale be long. The humming studies are consistent that the slow out-breath, not the pitch, is where the measurable autonomic change comes from; the humming resonance technique walks through finding and holding the tone, and the humming and binaural beats page gives a seven-step protocol and reads the Bhramari literature in full. Aim for an exhale of ten seconds or more and let the in-breath take care of itself.
3. Keep the tone quieter than your hum. If the speaker is louder than your voice you will stop hearing the beating that tells you whether you are in tune, and the exercise collapses into listening. Set it just loud enough to check against.
4. Finish in silence. Stop the tone for the last two or three minutes and sit with the breath you have been pacing. That is the part of the practice with evidence behind it, and it does not need the tone at all.

Done this way, 136.1 Hz is a pitch pipe for a breathing practice. That is a modest description and it is the accurate one. The pages on breathing exercises and sound and the vagus nerve go into the breathing side without the tone.

This page plays a tone. The app plays a chant. They are different things and we would rather say so than let the names blur.

The web tool above is a synthesised sine wave at exactly 136.1 Hz, generated by the Web Audio engine in your browser, with a volume control and a 10- or 20-minute stop. Twenty minutes is the cap on every free tool on this site. Nothing is downloaded, nothing is streamed and nothing is stored; close the tab and it is gone. The main generator adds beats, modes and a noise bed on the same engine, but rounds carriers to whole hertz, which is why this page exists separately.

The mobile app ships an Om chant as one of its ambient sounds, alongside singing bowls and a 528 Hz Solfeggio bed, in the meditation-aids category. That is a recording of a voice — a sustained chant with its harmonics and its breath in it — and it can be layered under any of the 44 presets with no session limit. If the thing you actually want is the sound of Om rather than the number attached to it, the chant is the closer match; if you want the reference pitch to hum against, the tone on this page is the exact one. Neither is a treatment for anything, and the app’s preset descriptions are held to the same claims policy as this page.