555 Hz benefits and the note behind the number

What are the claimed benefits of 555 Hz?

The benefits claimed for 555 Hz come from numerology, not from a test of the tone. Numerology reads 555 as an angel number for change, and Harmonance's page names the tone Change and Openness: an intention to listen with while something in your life is shifting. Videos elsewhere promise far more, and none of it rests on a study of a 555 Hz tone.

PubMed, the main index of medical research, lists no listening study of 555 Hz. What can be checked is below: where the number comes from, which note it lands on, what listeners made of the tones either side of it in the one study that came close, and what the 555 Hz page actually plays, measured from its own audio.

Where does the angel number 555 come from?

The idea of angel numbers is recent. Most sources credit it to the author Doreen Virtue and her book Angel Numbers, published by Hay House in 2005, as the Internet Archive's catalogue records it. In numerology an angel number is a number with repeating digits, read as a sign worth noticing.

The usual reading of 555 is change. In numerology, as Dictionary.com sums it up, 555 is "said to represent change, good luck, transformation, freedom, and personal growth". It is taken as a stronger form of 5, the number numerology links with adventure and curiosity, and the number five itself has carried meaning since the ancient Greeks.

As a tone, 555 Hz is the number read as a frequency: 555 waves of pressure a second. Hertz is a modern unit, so nobody in the tradition chose this pitch; the number came first. Every angel tone is made the same way, so the nine of them are 111 Hz and its whole-number multiples, and 555 Hz is exactly five times 111 Hz. The guide to angel numbers and their frequencies follows the whole family, and the 111 Hz guide starts at its root.

What note is 555 Hz?

555 Hz is very nearly a C sharp. With the A above middle C tuned to 440 Hz, the usual convention, each semitone is a twelfth of an octave, so the C sharp four semitones above that A is 440 × 2^4/12 = 554.37 Hz. 555 Hz sits 1,200 × log₂(555 ÷ 554.37) = 2.0 cents above it, where a cent is a hundredth of a semitone. Play the two together and they beat once every 1.6 seconds, since 555 minus 554.37 is 0.63 Hz.

That C sharp is C sharp 5, a little over an octave above middle C. Halve 555 Hz and you reach its lower octaves, 277.5 and 138.75 Hz, each just above the C sharp below. Sound travels about 344 metres a second in air at 20 °C, so one wave of 555 Hz is 344 ÷ 555 = 0.62 metres long.

Being five times 111 Hz also fixes its place among the other angel tones. 555 ÷ 444 = 1.25, the ratio 5 to 4, so 555 Hz sits a pure major third above the 444 Hz tone, the interval at the bottom of a major chord. A piano's major third is a little wider, 400 cents against the pure third's 386.3, which is why 444 Hz reads as an A tuned 15.7 cents sharp while 555 Hz lands almost exactly on C sharp. 528 Hz, the best known Solfeggio tone, sits 27 Hz lower, 86 cents below, a little less than a semitone.

What happened when researchers played tones near 555 Hz?

No study has played 555 Hz itself and asked what it does. The nearest is an online rating test at the Australian National University, in which 37 adults heard twelve pure tones for 20 seconds each and rated how happy, sad, calm and angry each one sounded (Kumar, Abhayapala and Samarasinghe, 2022). The tones were the nine Solfeggio numbers with 110, 220 and 440 Hz, so the two either side of 555 Hz were 528 and 639 Hz.

The higher the tone, the less calm it sounded. Read from the paper's graph of average ratings, 528 Hz scored about 3.3 out of 10 for calm and 6.2 for anger, and 639 Hz about 2.5 and 7.4, against 7.6 for calm at 220 Hz. The authors put it plainly:

the emotion class anger is triggered in a frequency range starting from 440 Hz to 528 Hz

The volunteers judged how each tone sounded, not how they felt. The tones always came in rising order and each was rated against its neighbours, so the highest tones sat at the angry end of every comparison, and most volunteers were young, with a median age of 27. 555 Hz was not among the tones. What the test does suggest is that a pure tone in this range is heard as bright and edgy more readily than as calm, which is worth knowing when you choose how to play it.

The wider field is not much further along. The US National Center for Complementary and Integrative Health sums up research on music in general:

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

What does the 555 Hz page play?

The 555 Hz page plays the tone in two ways, and Harmonance measured both from the page's own audio files: the pure tone the player loops, and the Strings arrangement at the page's own settings.

The numbers behind the chart

Octave band	Tone alone	Strings
2,220 Hz, two octaves up	0%	0.1%
1,110 Hz, one octave up	0.5%	2.1%
555 Hz, the tone itself	99.5%	13.2%
277.5 Hz, one octave down	0%	45.3%
138.75 Hz, two octaves down	0%	33.9%
69.38 Hz, three octaves down	0%	5.3%

Download the measurements (CSV)

With Strings off, the page plays the tone on its own, and 99.5% of the sound sits in the octave band around 555 Hz. It is not a perfectly pure sine: two faint overtones sit above it, at 1,110 Hz, 23.1 dB quieter, and at 1,665 Hz, 34.1 dB quieter, which the site's tone carries by design.

With Strings on, the note stays but the sound moves down. 45.3% of the energy lies in the band around 277.5 Hz, an octave below, and 33.9% around 138.75 Hz, two octaves below; only 13.2% stays near 555 Hz. The strings play a chord on C sharp. Their strongest line is 208.8 Hz, the G sharp a fifth above C sharp 3, and six notes of the C sharp major scale, C sharp, D sharp, F, F sharp, G sharp and A sharp, carry 94.2% of their energy. The exact 555 Hz tone still plays underneath, 35.8 dB below the music. The same six-step shape turns up on the 174 Hz page, starting there on F, as the 174 Hz guide shows, so it belongs to the strings' score, which the site pitches to each page's tone, and was not chosen for 555 Hz.

That move downwards meets the rating test halfway. The tones its listeners heard as calmest were the low ones, and the strings keep 555 Hz's note while putting most of its sound an octave or two lower. The test played pure tones, not strings, so this is a reason to try both versions and notice the difference, not a finding.

How long should you listen to 555 Hz, and how loud?

No study sets a length for 555 Hz; the rating test played each tone for 20 seconds. Harmonance's page suggests five to fifteen minutes to begin with, seated or lying down, and stopping whenever the tone stops feeling comfortable. Many people play it while thinking through a change, a decision or a new direction, which is what its number stands for.

Set the volume low before you press play, especially if you have just come from a low tone. The ear is far more sensitive at 555 Hz than near the bottom of its range, and is most sensitive between 2 and 5 kHz. The 555 Hz and 111 Hz page files play at the same level, yet by the standard equal-loudness model at the level Harmonance measures its sound against, the 555 Hz tone comes out at 62.7 phon and 111 Hz at 41.9 phon. That is about four times as loud to the ear for the same setting on your device.

Keep it low enough to talk over. Loud listening is the one risk that is well established. The US 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 555 Hz on Harmonance?

Press play on the 555 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, mostly an octave or two lower. Nothing plays until you press play, and no account is needed.

In Harmonance Studio you can set 555 Hz beside other tones and shape your own mix. Its neighbours in the family are 444 Hz, the pure third below it, and 666 Hz, and the angel number collection plays all nine. For another tone named for change, the 417 Hz guide follows the Solfeggio number that carries that theme.

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 555 could not be read. The pitch, the beat, the wavelength and the major third are arithmetic from the standard tuning convention and the speed of sound, worked in full above. The research on listeners is one online rating test of twelve pure tones that did not include 555 Hz, read for the two tones either side of it. The measurements of the 555 Hz page are Harmonance's own, made from the page's audio files, and the loudness figures come from the standard equal-loudness model, not from listeners. No listener's words are quoted here.

1. Internet Archive, catalogue record of Doreen Virtue (2005), Angel Numbers, Hay House: the book that named angel numbers.
2. Dictionary.com, 555 angel number: the usual reading in numerology, and where angel numbers come from.
3. UNSW Music Acoustics, note names and frequencies: A at 440 Hz, equal semitones, and how to count cents.
4. Hass, an acoustics primer: the speed of sound, Indiana University: 344 metres a second at 20 °C.
5. Kumar, Abhayapala and Samarasinghe (2022), frequency cues for human emotions, in Acoustics: 37 adults rating twelve pure tones, 528 and 639 Hz among them.
6. Wikipedia, equal-loudness contour: how the ear's sensitivity changes with pitch, and the phon.
7. National Center for Complementary and Integrative Health, music and health: the state of music research, and loud listening.
8. World Health Organization, safe listening: weekly limits and device volume.