Tuning fork healing: the sound and the evidence

Tuning fork healing is a sound practice: a practitioner strikes a metal fork and holds it near your ears, or sets its stem on your body, so you hear one clear, fading tone and feel its buzz. Forks are often tuned to 128, 136.1 or 528 Hz. The studies are few and small, and none has tested a fork on its own against a fair alternative.

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Fifteen yellow ribbons of light in dark space, brightest and most wave-like at the centre, settling and fading towards both edges — Fifteen ribbons in the yellow of 528 Hz, the tone this page plays. They are brightest at the centre, where the strike sits, and fade evenly to either side, the way a struck fork's tone fades.

What is tuning fork healing?

Tuning fork healing is a sound practice built on one small instrument. A practitioner strikes a metal tuning fork and holds it near your ears, or sets its stem on your body, so that you hear one clear, fading tone and feel its buzz. A large seller of sound healing instruments describes both ways of working: forks held "near the ears for focused listening", and forks set "on the body to transmit vibration" (Sunreed's guide).

Several named methods grew from it. Since Hans Cousto calculated tones from the orbits of the Earth and planets, forks have been made in them, and Planetware, which publishes his tuning data, describes "tone puncture, in which the tuning fork is placed on the body" (Cousto). In Biofield Tuning, practitioners move a struck fork through the space beside the body, "detecting off-the-body biofield perturbations using tuning fork (TF) vibrations" (Hammerschlag and colleagues). Solfeggio fork sets carry the numbers behind the Solfeggio collection, 528 Hz among them.

The tone a fork makes is real and easy to measure. The claims made for it are another matter, and very few have been tested. For the wider field, read the science of sound healing and its history.

How does a tuning fork make its sound?

Strike a fork and its two prongs, called tines, swing towards each other and apart again, hundreds of times a second. Daniel Russell of Penn State's Graduate Program in Acoustics puts it exactly: "The two tines of the fork alternately move toward and away from each other, each bending like a cantilever beam, fixed at the stem and free at the other end." The tines move as mirror images, and the number of swings each second is the fork's pitch (Russell).

The stem moves too. As the tines swing, "the stem actually vibrates up and down at the fundamental frequency as well as at the second harmonic", which is why a fork grows louder the moment its stem touches something; Russell suggests "touching the stem of a vibrating fork to a table top, door, or piano soundboard" to hear it. Held up on its own, a fork is quiet. Its steel is a poor match for the air, and the two tines push the air in opposite directions, so "those two opposite waves interfere", "largely cancelling each other" (Wikipedia). Pressed "against the bone just behind the ear", the stem carries its tone through the skull, a route that skips the middle ear and lets doctors test hearing, as a later section explains.

A tuning fork on a table: its two tines swing in and out as mirror images while its stem moves up and down at the same pitch — How a tuning fork makes its sound: the two tines swing in and out together as mirror images, the stem moves up and down at the same pitch and passes the sound into a table or bone, and a hard strike adds a high clang that soon dies away. Movement drawn far larger than life, after Russell.

A hard strike adds something else. Hitting the tines against a hard object sets off a second way of bending, the clang, at a frequency "roughly 6.26 times higher than the fundamental". For a moment it can sound louder than the fork's own note, because "the human ear is much more sensitive to frequencies between 1000 Hz and 4000 Hz" (Russell). Researchers who measured struck forks with a laser found that the fork's own pitch "was the dominant observed frequency in all testing scenarios", but when 256 and 512 Hz forks were struck on metal or wood, extra tones appeared that are not part of the note (Stevens and Pfannenstiel). That is the case for striking a fork on something softer, such as your knee or palm.

How long does a tuning fork ring?

A struck fork starts to fade the moment you strike it, and Harmonance measured one to show how fast. The recording is a 440 Hz fork struck once, 27 seconds long, which its maker placed in the public domain on Wikimedia Commons. Its tone sits at 440.2 Hz. From the strike it fades at a steady 1.3 dB a second: 9 dB down after 5 seconds, 16 dB after 10 and 38 dB when the recording ends. In decibels the fade is a straight line, so the fork loses the same share of its sound every second, and at that rate it would take about 45 seconds to fall by 60 dB.

The clang behaves very differently. In the first tenth of a second there is a second tone at about 2,700 Hz, 6.13 times the fork's pitch, close to the 6.26 times Russell gives. It starts 26 dB below the main tone, fades about 21 dB a second, some 16 times faster than the tone, and is gone within about 3 seconds. The fork's first overtone, at 880 Hz, sits 34 dB below its tone. That is why a fork sounds bright and metallic at the strike, then settles into what Wikipedia calls "a pure musical tone once the high overtones fade out".

Lines over 27 seconds: a struck 440 Hz fork fades 1.3 dB a second, its clang is gone in 3 seconds, and the 528 Hz tone here stays level — A struck tuning fork beside the steady tone on this page, measured by Harmonance: the 440 Hz fork's tone fades 1.3 dB a second, its clang at about 2,700 Hz fades about 21 dB a second and is gone in about 3 seconds, and the 528 Hz tone this page plays holds within 0.02 dB. Each line is set against its own recording's loudest moment.

The tone on this page works differently by design. Harmonance's 528 Hz recording is a steady tone that repeats every 20 seconds, and across that loop its level moves by 0.02 dB. A fork gives you a bright strike and a ring that fades within a minute; the player gives you one tone at one level for as long as you leave it on. They suit different moments: a fork for a single, focused strike, a steady tone for listening that lasts.

What frequencies are tuning forks tuned to?

Any pitch can be cut into a fork. "A tuning fork's pitch depends on the length and mass of the two prongs", and makers tune it with a file: "Filing the ends of the prongs raises the pitch, while filing the inside of the base of the prongs lowers it" (Wikipedia). The number on a fork says where it comes from.

The tones tuning forks are most often made in, and where each number comes from, drawn from the sources listed below.

Common tuning fork tones
Fork	Tone	Where the number comes from
Concert pitch	440 Hz	The A that many orchestras tune to, and today's most common fork
Hearing tests	512 Hz, or 256 Hz	The old scientific pitch, a C, which became medicine's standard
Vibration sense	128 Hz	A low C, set on bone to test whether you feel vibration
Solfeggio sets	174 to 963 Hz	Six numbers published in 1999, 528 Hz among them, later extended to nine
Om, or Earth year	136.1 Hz	The Earth's year raised 32 octaves, in Hans Cousto's calculation
Weighted body forks	128 Hz	Low C forks sold to be set on the body and felt
Biofield Tuning	174 Hz	The unweighted fork used in the one study of the method's agreement

The 528 Hz fork belongs to the Solfeggio set. Its numbers were published in 1999 and presented as found by someone "intuitively guided to find the pattern of six repeating codes in the Book of Numbers, Chapter 7, verses 12 through 83" (Tetrahedron press release). Fork makers followed: one seller's set was "tuned to the six missing frequencies of the Ancient Solfeggio", and its page asks "Why 6 forks when others have gone to 9?" (SomaEnergetics). For where each number comes from and what studies of them found, read the Solfeggio frequencies guide and 528 Hz benefits.

The 136.1 Hz fork comes from Hans Cousto, who raised the frequency of the Earth's year by 32 octaves, doubling it 32 times until it could be heard: "the 32nd octave of the Earth Year is a C# with 136.10 Hz" (Cousto). The Om frequency guide tells why it is called Om, and 136.1 Hz plays on its own page here.

What is the difference between weighted and unweighted forks?

Weighted forks are made to be felt, unweighted forks to be heard. Weighted forks "have small weights attached to the ends of the tines", and in a seller's words, "These weights increase how strongly vibration travels down the handle and into the body". Unweighted forks have none, and "their sound carries more clearly through the air" (Sunreed's guide). The same seller calls its 128 Hz weighted fork "both audible and easily felt through the body" and suggests setting it on the ribs, spine and breastbone (Sunreed).

The physics fits. A fork's pitch depends on the mass of its prongs, so added weight lowers it, and the stem is what passes the vibration on to whatever it touches. Doctors use the same idea. Their low forks test whether you feel vibration, and a graduated version, the Rydel-Seiffer fork, "assesses vibration sense semiquantitatively". In a study of 198 healthy people, tested on the finger, wrist, big toe and ankle, vibration sense declined with age at every one of those places (Martina and colleagues).

Where did the tuning fork come from?

From a trumpeter's injury. "It was 1711 when the tuning fork was invented", by John Shore, a trumpeter "who performed in the courts of King James II and played for George Frideric Handel". He "split his lip after a concert and was never able to play the trumpet again", took up the lute, an instrument that needs regular tuning, and "set out to create a solution, resulting in the invention of the tuning fork" (Eraniyan and Ganti; Wikipedia).

Musicians kept it for tuning: "the most common tuning fork sounds the note of A = 440 Hz, the standard concert pitch that many orchestras use" (Wikipedia). Doctors took it up in the 1800s. "The tuning fork reached its medical spotlight in 1834 when the Weber test was created", and the old scientific pitch of 512 Hz "came to be the standard pitch used in medicine" (Eraniyan and Ganti).

How do doctors use tuning forks?

As quick bedside tests, never as a remedy. Three uses are common.

Hearing: in the Rinne and Weber tests a doctor compares how you hear a fork through the air and through the bone behind your ear, to tell whether a hearing loss lies in the outer or middle ear or further in, along the nerve pathway. In a survey of 116 doctors, 73 per cent used a 512 Hz fork, 46 per cent struck it on the knee and 45 per cent held it 3 to 4 cm from the ear (Butskiy and colleagues). A review of 17 studies with 3,158 people found the tests far from exact: the Rinne test picked up hearing loss of the outer or middle ear in 43 to 91 per cent of cases with a 256 Hz fork, and 16 to 87 per cent with a 512 Hz fork (Kelly, Li and Adams).
Nerves: a 128 Hz fork checks "vibration sense as part of the examination of the peripheral nervous system" (Wikipedia), and the graduated fork above puts a number on it (Martina and colleagues).
Broken bones: a vibrating fork, most often 128 Hz, set near a suspected fracture has been tried as a quick check. A review of six studies with 329 patients found these tests "have some value in ruling out fractures, but are not sufficiently reliable or accurate for widespread clinical use" (Mugunthan and colleagues).

So the fork has a long, respectable life in medicine as a way of checking hearing and nerves. That is a different claim from healing, and the evidence for one says nothing about the other.

Does tuning fork healing work?

Nobody has shown that it does, and very little has been tested. A search of PubMed, the index of medical research run by the US National Library of Medicine, for tuning forks in sound healing, sound therapy, biofield or acupoint work finds four studies. None compares a fork on its own with a fair alternative.

The first asked whether practitioners agree. Three Biofield Tuning practitioners each used "an activated 174 Hz unweighted" fork to comb the same four places beside 10 volunteers, calling out where they sensed disturbances. Allowing 2 inches either way they agreed 33 per cent of the time, and the statistics "strongly supported the conclusion of poor" agreement (Hammerschlag and colleagues).

The second gave 15 people with high scores on a questionnaire for feeling anxious three weekly, hour-long Biofield Tuning sessions at a distance, over Zoom. Their scores for feeling anxious, for negative mood and for stress fell. But there was no comparison group, so the study cannot separate the sessions from time, attention or expectation, and 2 of the 15 left after the first session. The chief executive of BioSona, the company that trains the practitioners, was one of the authors, and her institute helped secure the funding (Jain and colleagues). The third interviewed 12 of the same people, who "were surprised by the degree to which they felt sensations and heard tuning fork changes" (Sprengel and colleagues).

The fourth, a randomised trial by researchers in Hong Kong, gave 46 students with mild distress three sessions of 30 to 35 minutes combining singing bowls, tuning forks and a magnetic massage along the meridians of Traditional Chinese Medicine, against calming music or an audio story. Stress scores and heart rate fell further with the combined sessions, but the forks were never tested on their own, so their part cannot be told apart from the bowls, the massage and the attention (Lam and colleagues).

One popular claim needs its own note. A large seller's page for a 128 Hz weighted fork says it "has even been shown to increase the release of nitric oxide" and names no study (Sunreed). The nearest published work is a 2003 paper that proposed nitric oxide as the molecule behind music's relaxing effects; it describes no experiment with a fork (Salamon and colleagues). In PubMed, the two papers that mention tuning forks and nitric oxide together are about laboratory sensors.

What this adds up to: a struck fork is a simple, pleasant sound, and people in these small studies reported sensations and feeling calmer. No study has shown that a fork does more than that, or that one frequency works better than another. The fair way to approach a fork session is as a listening experience, and to judge it by how it feels to you.

How loud is a tuning fork, and is it safe for your ears?

Close to the ear, louder than you might expect. Researchers held 512 and 256 Hz aluminium forks 30 to 49 mm from a model ear and measured each strike over 3 seconds. With the tines in line with the ear canal, the louder of the two positions they tried, the 512 Hz fork averaged 90.04 dB at the model's eardrum in its own pitch band, and the 256 Hz fork 91.14 dB (Butskiy and colleagues). The World Health Organization's guide is that "If the sound level is 90dB, the safe listening time reduces to four hours per week" (WHO).

A fork's ring is short, though. A level that falls 1.3 dB a second, as the fork Harmonance measured does, carries the sound energy of about 3 seconds at its starting level, so one strike by your ear uses a sliver of that weekly allowance. A few habits keep it comfortable: hold the fork a few centimetres from your ear, as doctors do, rather than against it; strike it on your knee or palm rather than a table, which adds extra tones; and if you have tinnitus or find some sounds hard to bear, tell the practitioner first and ask them to keep the fork further away.

How can you try tuning fork sound at home?

Start with the tone. Press play at the top of this page for 528 Hz, one of the Solfeggio fork tones, held steady instead of fading, or open 528 Hz on its own page and the rest of the Solfeggio collection, from 174 to 963 Hz. If you have a fork, a few simple listening experiments show everything this guide describes.

Listen for the fade: strike it on your knee, hold it a few centimetres from one ear and follow the tone until you lose it. The bright clang goes first; the pure tone lingers.
Turn it slowly: rotate the ringing fork beside your ear. Its loudness rises and falls with the angle, because a fork "radiates sound as a lateral quadrupole source", stronger in some directions than others (Russell).
Hear the stem at work: strike it again and touch the stem to a wooden table. The tone jumps louder, because the table's broad surface passes the vibration to the air.
Pair it with the player: play 528 Hz quietly from a speaker and strike your fork beside it. A fork a few hertz away from the tone will beat against it, the sound swelling and fading as the two fall in and out of step, as the sound bath guide explains for singing bowls.
Build a longer session: in Studio, free once you sign in, you can layer tones and set a timer.

Keep it gentle: you should still hear your own breathing over the tone. For patterns that sound draws in sand and water, see cymatics.

Sources and limits

Harmonance measured one recording of one 440 Hz fork, made by someone else with an unknown microphone in an unknown room. Other forks, struck harder or softer, ring longer or shorter, and the chart's levels are relative to each recording, not sound levels at your ear; the clang's end is where it sinks into the recording's own noise. The studies of fork sessions are few and small: the two Biofield Tuning studies had no comparison group and involved people connected to the method, and the one randomised trial combined forks with bowls and massage. The PubMed search looked for tuning forks with sound healing, sound therapy, biofield or acupoint in a title or abstract. No study has tested the 528 Hz tone on this page, and Harmonance's measurement of it describes the recording, not its effects.