Remove clicks and crackle from vinyl and tape rips.

At a glance

How to remove clicks from a vinyl rip

Record the side as you normally would, from a USB turntable such as an Audio-Technica AT-LP120XUSB, or a deck through a phono preamp into an audio interface, ideally as a 24-bit WAV. Drop the file here, leave the sensitivity on Normal and press Remove the clicks. The report says how many clicks were repaired and how much of the recording that touched, which is usually a few hundredths of one percent, so everything you are keeping is exactly as you recorded it. The output is the same length and the same format as the rip, so you can split it into tracks afterwards with the splitter.

Clean the record before you rip it if you can. A wet clean, even with a brush and a fluid, removes the dust that makes most of the crackle, and no software repairs a click as well as not having it. Scratches that the stylus jumps, and pops large enough to be heard as a thump, are beyond any click remover; for those, cut the bad moment out in the editor, or copy the same bar from a later repeat over it.

How it finds a click

Music is predictable a fraction of a millisecond ahead: from the last 32 samples you can predict the next one very closely, because instruments and voices are made of sustained vibrations. A click is a speck of dust or a scratch striking the stylus, and it is not predictable at all. So the page fits a predictor to each tenth of a second of the recording and watches the prediction error. A click is where the error jumps far above its own level in the surrounding 20 milliseconds. Its end is found the same way, predicting backwards from the samples after it. Measuring against the local level is what keeps a hi-hat, a snare or a sibilant from being taken for a click: they raise the error around themselves, so the bar rises with them.

Two more rules keep real sound safe. A click is short, so anything flagged for more than 2.5 milliseconds is left alone. And a click stops: if the prediction error stays high after the flagged moment, it was the start of a drum hit or a consonant, not a defect, and it is not touched. In the check behind this page, 30 seconds of clean drums (kicks, snares and hi-hats) had no sample touched, and clean speech none.

How it repairs one

The flagged samples are thrown away and rebuilt by least-squares autoregressive interpolation, the method Simon Godsill and Peter Rayner set out for restoring old recordings: the missing samples are chosen to be as predictable as possible from the music on both sides. The model for each repair is fitted on the 40 ms around the click with the click itself left out, so a loud pop does not bend the model that fills it. It uses 128 coefficients, enough to carry a chord: in the check, 32 coefficients left a repaired click 14.7 dB quieter and 128 left it 22.7 dB quieter. The page makes a second pass over the repaired sound, so crackle packed closely together is found against a cleaner background.

The check plays chords with bass and drums, and spoken word, each over a transfer's noise floor at -60 dBFS, with clicks built the way a record player makes them: one to four impulses through RIAA de-emphasis, plus the cartridge's resonance ringing at 6 to 16 kHz. At the Normal setting it finds 75 of the 77 clicks louder than -14 dBFS in the music and all 55 in the speech. The few it misses land exactly on a drum hit, where the rule that a click must stop holds it back. The median repaired click is 16 dB quieter than it was.

Which setting to use

Normal suits most rips. Gentle repairs only clicks that stand far out, for a clean pressing with a few ticks, or for music with lots of sharp percussion. Strong also takes fine crackle, the frying sound of a worn or dusty record and of 78s, at a higher chance of nibbling at very sharp transients; listen to the cymbals afterwards. Audacity's Click Removal works on a similar idea with a threshold and a maximum spike width. Dedicated tools such as iZotope RX De-click and De-crackle, Brian Davies' ClickRepair and Adobe Audition's Automatic Click Remover are the paid way to go further.