Online tuning fork strike it, hold it, tune to it

How to use an online tuning fork

Choose a fork, then press Strike or Hold tone. The page offers seven forks, 440, 432, 256, 512, 128, 528 and 4,096 Hz, and a box for any frequency from 16 to 12,000 Hz. Strike plays the fundamental with a short clang partial at about 6.25 times the frequency and lets it fade, the way a struck steel fork behaves. Hold tone plays the same note steadily, which is easier when you are tuning an instrument or comparing two sounds.

Start quietly and raise the volume slowly. The World Health Organization advises keeping device volume at no more than 60 % of maximum, and that matters most for the high forks: 4,096 Hz sits inside the range where human hearing is sharpest, between about 2,000 and 5,000 Hz, so it can sound much louder than 128 Hz at the same setting.

Use headphones or a proper speaker for the low forks. Phone and laptop speakers are too small to move much air at low frequencies, so a 128 Hz tone may sound thin or partly vanish on them, while a pair of headphones plays it fully.

How does a tuning fork work and why is its tone so pure

A tuning fork is a U-shaped steel bar on a stem. Strike a prong and the two prongs swing towards and away from each other at one fixed rate, its frequency. A 440 Hz fork vibrates 440 times a second, and the sound wave it sends out is about 78 cm long in air at 20 °C, where sound travels at about 343 m/s.

The tone is pure because the shape puts almost all the energy into the fundamental. The first overtone, called the clang tone, is about 6¼ times the fundamental, roughly two and a half octaves higher. Little energy goes into it and it dies away faster, so after a moment you hear an almost perfect sine wave. That is the brief metallic ping at the start of every strike, followed by the clean hum.

Held in open air, a fork is faint, because its thin prongs push little air. Press the stem against a table, a guitar body or a bone and the tone becomes much louder: the larger surface vibrates with it and radiates the sound. Doctors rely on exactly this when they place a fork on the skull or on a bony point of the foot.

A curious result of the 6.25 rule: on a real 4,096 Hz fork the clang tone lies around 25.6 kHz, above the textbook upper limit of human hearing of 20 kHz, so people hear only the pure fundamental.

What frequency is a standard tuning fork? A440 explained

A standard tuning fork is A440: it sounds the A above middle C at 440 Hz. The international standard ISO 16:1975, "Acoustics: Standard tuning frequency (Standard musical pitch)", specifies 440 Hz for the note A in the treble stave, to an accuracy of 0.5 Hz, and it remains confirmed today.

The number has a history. France fixed its A at 435 Hz on 16 February 1859; delegates of five countries agreed on 440 Hz in London in May 1939; ISO took it up in 1955 and confirmed it as ISO 16 in 1975. The full story, including the arguments for 432 Hz, is on the page 432 Hz vs 440 Hz, so it is not repeated here.

A440 is the 49th key of an 88-key piano. Every other note follows from it in equal temperament, where each semitone is 2^(1/12), about 6 %, higher than the one below and twelve semitones double the frequency. That is why one A fork is enough to tune a whole instrument by ear.

Tuning fork frequencies: which fork is used for what

Forks come in two families. A musical fork usually sounds A440, the standard pitch. Medical and scientific forks are usually C-based, 128, 256, 512 Hz and so on, because they follow "scientific pitch", in which every C is a power of 2. The table compares the forks on this page with the nearest note in standard A440 tuning, measured in cents (hundredths of a semitone).

The C forks all sit the same 37.6 cents below modern pitch because they belong to one system: C = 256 Hz. A musician who tunes a guitar to a 512 Hz medical fork will end up about a third of a semitone flat compared with a piano at A440.

Who invented the tuning fork?

The tuning fork was invented in 1711 by John Shore, an English trumpeter and lutenist who served as sergeant trumpeter to the royal court. The fork Shore gave to George Frideric Handel is said to sound C = 512 Hz, which shows how far pitch has moved since: on a modern A440 piano that C is 523.25 Hz.

Only two years later, in 1713, the French scientist Joseph Sauveur proposed setting middle C at exactly 256 Hz. In that "scientific pitch", also called Sauveur pitch or "Verdi tuning", A comes out at about 430.54 Hz. Orchestras never adopted it, but it remained handy in science because each C is a power of 2: 128, 256, 512, 1,024 and so on up to 4,096 Hz.

Music went the other way. After France's A = 435 Hz of 1859 and the London agreement of 1939, ISO 16 settled on A = 440 Hz, which puts middle C at about 261.63 Hz. Medical forks, by contrast, kept Sauveur's C-based numbers, which is why a doctor's fork reads 128 or 512 Hz rather than a note of the piano.

128 Hz tuning fork: what is it used for in medicine

The 128 Hz fork tests vibration sense, which travels along large nerve fibres in the feet and hands. The American Diabetes Association's 2017 position statement on diabetic neuropathy says screening should include a careful history, temperature or pinprick sensation, and vibration sensation using a 128 Hz tuning fork, plus an annual 10 g monofilament test. Screening starts at the diagnosis of type 2 diabetes and five years after the diagnosis of type 1, then at least once a year.

In practice the doctor strikes the fork and places it on a bony point, typically the tip of the big toe, and asks whether you feel the buzz and when it stops. In an Austrian study of 2,022 consecutive people with diabetes, the 128 Hz fork at both big toes found abnormal vibration sense in 105 of them (5.2 %), and it detected neuropathy reliably compared with an electronic neurothesiometer.

A graduated version, the Rydel-Seiffer fork, measures vibration sense semi-quantitatively: instead of a plain yes or no, the examiner reads a value from a scale. In a 1998 study of 198 healthy people and 59 patients with polyneuropathy, vibration sense declined with age at every site, the fork agreed with an electronic device, and sensitivity ranged from 29 to 76 % depending on the site, best at the big toe.

An online fork cannot do this test: vibration sense needs a steel fork pressed on bone, not sound from a speaker. The 128 Hz tone here lets you hear the pitch, nothing more.

512 Hz tuning fork: the Rinne and Weber hearing tests

Doctors use 512 Hz and 256 Hz forks for two quick bedside hearing tests. In the Weber test the fork is placed on the middle of the forehead and you say in which ear the sound is louder. In the Rinne test the doctor compares how well you hear the fork through the air next to the ear with how well you hear it through the bone behind the ear. Together they help tell conductive hearing loss, a problem in the outer or middle ear, from sensorineural loss in the inner ear or nerve.

How accurate are they? A 2018 systematic review of 17 studies with 3,158 participants found that the Rinne test for conductive loss had a sensitivity of 43–91 % and a specificity of 50–100 % with a 256 Hz fork, and a sensitivity of 16–87 % and a specificity of 55–100 % with a 512 Hz fork. The Rinne test turns abnormal only once conductive loss reaches 13–40 dB.

So the forks are a useful first look, but an audiogram with an audiometer remains the reference. Like the vibration test, these tests depend on a fork touching the skull, which no speaker or headphone can imitate.

Can a tuning fork detect a fracture?

A 128 Hz fork is sometimes used to screen for a broken bone by vibrating the bone near the injury. The evidence is weak. A 2014 systematic review in BMJ Open pooled six studies with 329 patients and found a sensitivity of 75–100 % and a specificity of 18–95 %; the fork had some value for ruling a fracture out but was "not sufficiently reliable or accurate for widespread clinical use".

A later study in 63 soldiers with suspected stress fractures of the shin bone compared the fork with MRI and found a sensitivity of 61.5 % and a specificity of 25 %, calling it "an ineffective tool". In that study MRI was the reference, and imaging remains the way to confirm a fracture.

Tuning forks for healing and sound therapy: what the evidence says

Tuning forks are widely sold for sound healing, and they are used in alternative practices such as sonopuncture and polarity therapy. A search of the medical literature on 1 October 2026 found no controlled trial of tuning-fork healing or tuning-fork sound therapy. The medical uses described above are tests, not treatments.

The same applies to the popular frequencies. Forks sold at 528 Hz or 432 Hz have never been tested in a study as forks. A few small studies have looked at music tuned to 432 Hz or at 528 Hz music; what they found, and how strong it is, is set out on the 528 Hz page and on the 432 Hz vs 440 Hz page.

None of this makes a fork useless for a personal ritual. A struck fork gives a clear, fading tone that is easy to follow with attention, and many people use it to mark the start and end of a quiet moment. Just keep the two things apart: the experience is yours, while the healing claims have not been tested.

How to tune a guitar with a tuning fork

Use an A440 fork and tune one string to it, then tune the other strings to that one. Standard guitar tuning runs E2, A2, D3, G3, B3, E4 from the thickest string, and the fork's A4 relates simply to two of them: the open A string (A2, 110 Hz) is exactly two octaves below 440 Hz, and the high E string played at the 5th fret gives A4, 440 Hz itself.

The trick is to listen for beats. When two tones are close but not equal, their sum swells and fades at a rate equal to the difference between them: 440 Hz against 442 Hz wobbles twice a second. Turn the tuning peg so that the wobble slows down; when it disappears, the string is in tune.

• Press Hold tone on the 440 Hz fork, or strike a steel fork and press its stem on the guitar's body or bridge so the guitar amplifies it.
• Play the high E string at the 5th fret. Listen for the beating against the fork and turn the peg until it stops.
• If you prefer the A string, play its natural harmonic at the 5th fret: touch the string lightly over the fret wire and pluck. It sounds A4, the same pitch as the fork.
• Tune the rest by the usual relative method: 5th fret against the next open string, except the G string, where the 4th fret gives B.
• For 432 Hz tuning, do the same with the 432 Hz fork; the whole guitar ends up 31.8 cents lower than standard.

Beats are easiest to hear with a steady tone, which is why Hold tone suits tuning better than Strike. Keep the guitar note and the fork at similar loudness.

Online tuning fork or a real one: what can each do

An online fork reproduces the sound: the same pitch, the short clang at the start and the fading tone. It costs nothing, it offers any frequency from 16 to 12,000 Hz, and it never goes out of tune, because the frequency is a number in software. For tuning an instrument by ear, teaching what pitch and octaves are, or simply hearing what a 128 Hz or 4,096 Hz fork sounds like, it does the job.

A steel fork does what sound from a speaker cannot: it vibrates against the body. The 128 Hz neuropathy test, the Rinne and Weber tests and the fracture test all need that physical contact, which is why clinicians use real forks and why no online fork should be used in their place. The speaker also shapes what you hear, so a low fork may sound weaker on a phone than through headphones.