333 Hz frequency meaning and how it sounds

What does 333 Hz mean?

333 Hz means 333 waves of sound a second, and its meaning as an angel tone comes from the number, not from the sound. In numerology, as Dictionary.com sums it up, the angel number 333 is "said to represent creativity, good luck, positivity, growth, and good communication". The number 3 stands for creativity, charm, communication and optimism, and 333 is read as a stronger 3.

Harmonance's own page calls the tone Self Expression, from the same reading. None of these meanings comes from a test of the tone, and some videos promise far more than any study has looked at. What can be checked is below: where the number comes from, which note 333 Hz really is, why it sits so easily beside 111 and 222 Hz, the two studies that used it as a test sound, and what the 333 Hz page plays, measured from its own files.

Where does the angel number 333 come from?

From a modern reading of an old idea. The number 3 "has been seen to have mystical significance since the time of the ancient Greeks", Dictionary.com notes, but angel numbers themselves are recent: "Most sources credit the idea of angel numbers to author Doreen Virtue, who wrote about their significance in her 2005 book Angel Numbers." The book's catalogue record at the Internet Archive gives its full title, with 111 and 444 in the subtitle.

As a tone, 333 Hz is the number read as a frequency. Hertz is a modern unit, so the tradition never chose this pitch: the number came first, and the tone carries it into listening. The guide to angel numbers and their frequencies covers the whole family, and the 888 Hz guide looks at why repeating numbers seem to turn up so often.

What note is 333 Hz?

333 Hz is not a note of the piano: it falls just above E4, the E above middle C. With A tuned to 440 Hz and twelve equal semitones to the octave, as UNSW's music acoustics tables set out, E4 is 329.63 Hz and F4 is 349.23 Hz. 333 Hz is 17.6 cents above E4, where a cent is a hundredth of a semitone, so it is much closer to E than to F, and in tune with neither.

Two comparisons make the number concrete. Play 333 Hz beside E4 and the two differ by 3.37 Hz, so the sound swells and fades 3.37 times a second. And the E a pure fifth above the A at 220 Hz is exactly 330 Hz: 333 Hz sits 15.7 cents above it, the same distance 111 Hz sits above the A at 110 Hz, because 333 and 330 are 111 and 110 multiplied by three.

One wave of 333 Hz lasts 3.003 milliseconds. The tone also sits inside the range where human hearing is keenest: an acoustics primer from Indiana University puts our greatest sensitivity between about 200 and 2,000 Hz, a range 333 Hz is inside and 111 Hz is not.

Why does 333 Hz sit so easily with 111 and 222 Hz?

Because 333 is 111 times three. In the harmonic series of 111 Hz, the run of frequencies at one, two, three and more times the lowest, 222 Hz comes second and 333 Hz third. Against 222 Hz, 333 Hz makes a ratio of 3 to 2, the perfect fifth; the fifth of a piano tuned in equal steps is, in the primer's words, "very close to the 3:2 ratio it would have in the just intonation system", about 2 cents narrower. Against 111 Hz, 333 Hz lies an octave and a fifth above.

The same series lives inside single sounds. Any steady sound with a pitch can be built from sine waves at whole-number multiples of its lowest frequency, an idea the primer's chapter on timbre traces to Fourier, and the balance between them is much of what makes an instrument sound like itself. The site's 111 Hz tone carries a faint 333 Hz overtone, 34 dB below the tone, as the 111 Hz guide measured, and the 333 Hz page's own tone carries faint lines at 666 and 999 Hz, measured below.

Listeners tend to like intervals built this way. In tests with more than 250 people, McDermott, Lehr and Oxenham found that a liking for sounds whose frequencies line up in a harmonic series went with a liking for consonant chords, while a dislike of beating did not (Current Biology, 2010):

Listeners preferred stimuli without beats and with harmonic spectra, but across over 250 subjects, only the preference for harmonic spectra was consistently correlated with preferences for consonant over dissonant chords.

The study was about chords in general, not 333 Hz. What it adds here is simple: every angel tone is a multiple of 111 Hz, so any two of them line up in one harmonic series, the property the listeners in that study preferred.

Has anyone studied 333 Hz?

Not as an angel tone, and not for anything people say it brings. PubMed, the main index of medical research, lists 58 records that mention 333 Hz, and nearly all of them are settings for electrical stimulation or laboratory equipment. Two are studies of hearing that used 333 Hz as a test sound, and what they found is about how the ear and brain follow a tone, not about creativity or luck.

19 adults and a sound at 333 Hz, 2021

When you hear a steady tone, neurons along the hearing pathway fire in step with its waves, and sensors on the scalp can pick that up as the frequency-following response. A team in Barcelona and Jyväskylä recorded it in 19 healthy adults listening to sounds at 89 Hz and at 333 Hz (Gorina-Careta and colleagues, 2021), using magnetoencephalography to find where in the brain it came from:

Our results showed that the main contribution to the high-frequency sound FFR originated in the inferior colliculus and the medial geniculate body of the thalamus, with no significant cortical contribution.

In plain words: at 333 Hz the wave-by-wave response came from relay stations deep in the brain, in the midbrain and the thalamus, while at 89 Hz the auditory cortex near the surface took part as well. That fits an earlier study by Coffey and colleagues in 2016, who saw the cortex join in at 98 Hz and noted that "neurons within the AC have an upper limit to phase-locking of about 100 Hz", AC being the auditory cortex. 333 Hz is simply too fast for the cortex to follow wave by wave.

20 people listening for a hidden pitch, 2005

In Tübingen, Hertrich and colleagues hid pitches of 333 and 400 Hz inside noise and asked 20 people to identify them while recording their brain activity (NeuroReport, 2005). The brain's response to a pitch appearing peaked about 180 milliseconds after it began, and its first stage was stronger for 400 Hz than for 333 Hz. Here 333 Hz was one of two pitches to tell apart, chosen for the experiment and not studied for itself.

What the two add up to

Both studies show the hearing system tracking a 333 Hz sound closely, which it does for any steady tone in this range. Neither measured how the sound made anyone feel, neither is about the angel number, and the 2021 summary does not say what the sounds were beyond their frequency, how loud they were or how long they lasted. For music and health more widely, the US National Center for Complementary and Integrative Health sums up where research stands:

However, because much of the research on music-based interventions is preliminary, few definite conclusions about their effects have been reached.

So take 333 Hz for what it is: a clear, steady tone in the most sensitive part of your hearing, with a number many people find meaningful. If you play it while you write or make something, notice what it does for you, and keep that as your own experience rather than a measured effect.

What does the 333 Hz page play?

The 333 Hz page plays the tone in two ways, and we measured both from the page's own audio files: the tone alone, and the tone under a strings arrangement.

Share of each sound's energy, by octave band

Octave band	Tone alone	Strings
5,328 Hz, four octaves up	0%	0%
2,664 Hz, three octaves up	0%	0%
1,332 Hz, two octaves up	0%	1.5%
666 Hz, one octave up	0.5%	14.0%
333 Hz, the tone itself	99.5%	51.6%
166.5 Hz, one octave down	0%	23.3%
83.25 Hz, two octaves down	0%	9.6%

Download the measured spectra (CSV)

Download the octave band shares (CSV)

With Strings off, 99.5% of the sound lies in the octave band around 333 Hz. It is not a perfectly pure sine: two faint overtones sit above it, at 666 Hz, 23.1 dB quieter, and at 999 Hz, 34 dB quieter, which the site's tone carries by design. Both are angel tones in their own right.

With Strings on, the sound spreads out: 51.6% of it lies in the band around 333 Hz, 23.3% an octave lower around 166.5 Hz, 14.0% an octave higher and 9.6% two octaves down. The strings play a chord built on 333 Hz. Their eight strongest lines, at 110.8, 124.5, 140.0, 209.1, 249.1, 333.1, 373.9 and 497.4 Hz, are 333 Hz itself with the second, third, fourth, fifth and sixth notes of a major scale built on it, the fifth in three octaves. The strongest of all is 373.9 Hz, a whole tone above 333 Hz, and the lowest, 110.8 Hz, falls within a fraction of a hertz of 111 Hz. The exact 333 Hz tone still plays underneath, 35 dB below the music.

How long should you listen to 333 Hz, and how loud?

No study sets a length for 333 Hz. Harmonance's page suggests five to fifteen minutes to begin with, seated or lying down, with a notebook nearby in case an idea comes loose, and you can stop whenever it no longer feels comfortable.

Keep the volume low, low enough to talk over. Because 333 Hz sits where hearing is most sensitive, it carries clearly at a lower level than a deep tone such as 111 Hz. Loud listening is the one risk that is well established: the National Center for Complementary and Integrative Health notes that "listening to music at too high a volume can contribute to noise-induced hearing loss", and the World Health Organization's safe listening advice is that "you can safely listen to a sound level of 80dB for up to 40 hours a week", with your device's volume at no more than 60% of maximum.

How do you listen to 333 Hz on Harmonance?

Press play on the 333 Hz page. With Strings off it plays the tone alone; switch Strings on beside the player and the strings carry the same note as a chord. Nothing plays until you press play, and no account is needed.

In Harmonance Studio you can set 333 Hz beside other tones and hear the intervals for yourself: with 222 Hz it makes a perfect fifth, and 666 Hz is its octave. The angel number collection plays all nine angel tones, and the 111 Hz guide tells the story of the first of them.

For the wider field, what the science of sound healing shows sets out what research on sound and music has and has not found.

Sources and limits

The meaning of the number rests on a dictionary's summary of numerology and the catalogue record of the book that named angel numbers; the book's own words for 333 could not be read. The note arithmetic uses equal temperament with A at 440 Hz. The research is two hearing studies that used 333 Hz as a test sound, read in their published summaries, with a 2016 study read in full for context; none tested how 333 Hz affects anyone, and the study of harmony is about chords in general. The measurements of the 333 Hz page are Harmonance's own, made from the page's audio files.

1. Dictionary.com, 333 angel number: the usual reading in numerology, and where angel numbers come from.
2. Internet Archive, catalogue record of Doreen Virtue (2005), Angel Numbers, Hay House.
3. UNSW Music Acoustics, note names, MIDI numbers and frequencies: A at 440 Hz, equal semitones, and how to count cents.
4. Hass, an acoustics primer: pitch and tuning, Indiana University: where hearing is most sensitive, and the fifth as 3 to 2.
5. Hass, an acoustics primer: timbre, Indiana University: harmonic partials and Fourier.
6. McDermott, Lehr and Oxenham (2010), individual differences reveal the basis of consonance, in Current Biology: more than 250 listeners.
7. Gorina-Careta and colleagues (2021), neural generators of the frequency-following response to low and high frequency sounds, in NeuroImage: 19 adults, 89 and 333 Hz.
8. Coffey and colleagues (2016), cortical contributions to the auditory frequency-following response, in Nature Communications: the cortex at 98 Hz.
9. Hertrich and colleagues (2005), brain responses to pitch hidden in noise, in NeuroReport: 20 people, 333 and 400 Hz.
10. National Center for Complementary and Integrative Health, music and health: the state of music research, and loud listening.
11. World Health Organization, safe listening: weekly limits and device volume.