Hearfork

What Hearfork trains

Hearfork measures and trains the fine end of your pitch sense: the just-noticeable difference, the smallest pitch gap you can reliably hear, reported in cents. A cent is one hundredth of a semitone, so the numbers here describe differences far smaller than any note name can. It is a resolution test, not a knowledge test: nothing is named and nothing is compared to a scale. You only have to notice that one tone does not belong, then say which way it leaned.

How to play

Each round shows three pads. Play the three tones plays all three in sequence, or tap a pad to hear that tone on its own: the first tap plays it, and a second tap picks it. Two tones are identical; the third is detuned. Pick the odd one out, and the true odd tone is marked whether or not you found it.

Then comes step two: how different was it? A five-notch scale runs from much lower through barely any difference to much higher, and you confirm your estimate. There are five rounds, and the detuning shrinks every time: 50 cents, then 30, 18, about 11 and finally about 6. The first round is roughly a quarter-tone and unmistakable; the last is finer than most instruments are ever tuned. The scale works from the arrow keys too.

How scoring works

Each round is worth 100 points, split three ways: 50 for finding the odd tone, 25 for the direction, and 25 for the size, with full marks for the right notch and partial credit one notch out. The five rounds are averaged into a score out of 100.

The headline number is different. Your threshold is the smallest detuning in which you still called the direction correctly, so it rests on the direction judgment alone. Miss the direction even in the 50-cent round and the result reads "> 50 cents". A threshold of 16 cents or better earns the day toward your streak.

What your score means

Read the threshold as a rough band, not a measurement:

Because the threshold rests on a single round, one lucky call moves it a whole step. The trend across many days is the honest signal.

Common mistakes

The biggest one is judging from a single pass. Replay the trio freely, and use the pads to hear one tone twice in a row, because the comparison is far easier when the tones are adjacent in time. Second, guessing the direction at random after finding the odd tone: that is the judgment your threshold is built on, so it is worth the extra listen. Third, playing too quietly, which flattens fine differences. Fourth, expecting the odd tone to be higher; it is lower half the time.

Practice progression

(5 min, beginner) play the daily five rounds on headphones in a quiet room, replaying each trio at least twice. (10 min, intermediate) use the practice tab: the hard tier starts at 36 cents and shrinks faster, and up to seven rounds pushes the last one below 3 cents. (weekly) pair it with Heardrift, which asks you to act on small differences in real time, and Hearkle, which puts the same fine judgment on a single daily target.

The science behind it

Pitch resolution comes from two mechanisms working together. The cochlea separates frequencies by place along the basilar membrane, which sets a coarse limit, and below roughly 4 kHz the auditory nerve also fires in step with the waveform, so spike timing carries the frequency far more precisely than place alone could. Fine discrimination is usually attributed to that temporal code. Thresholds are expressed in cents because the ear works logarithmically: the same interval spans very different numbers of hertz at the bottom and top of the range. Resolution improves with practice, especially in the first sessions. That is perceptual learning, not a change in the ear. See our guides to the just-noticeable difference and cents.

Limitations

Hearfork is a game and an informal self-check, not a clinical or diagnostic tool. It says nothing about hearing loss, which shows up as reduced sensitivity and clarity rather than as coarse pitch resolution. Browser audio, headphones and background noise all vary, so results from different devices are not comparable, and five rounds is far too few to be a measurement in the laboratory sense.

Where it shows up

Fine pitch resolution is what separates "close enough" from properly in tune. A violinist has no frets, so every note is placed by ear; a finger a millimetre off is a handful of cents out, and in a slow exposed passage that is audible to the room. A singer holding a long note against a piano hears the beating between the two and pulls back into line. A choir drifting a few cents flat over a phrase sounds tired rather than wrong, and the singers who notice small differences catch it first. A piano tuner works entirely in this territory, deliberately setting octaves slightly wide because that is what sounds right. Guitarists meet it every time they check the twelfth-fret harmonic against the fretted note. Outside music, the same resolution tells you a motor is running slightly slow, or that a familiar voice on the phone is not quite the voice you expected. In all of these, nobody names a note. They simply notice a difference that a coarser ear would let pass, and that noticing is the skill Hearfork puts a number on.

Related reading & games

• The just-noticeable difference: what the number means.
• Cents and hertz: the two units in play.
• Heardrift and Hearkle: the same judgment, applied.
• All ear-training guides.