Fix clipped, distorted audio online

What clipping is and how to spot it

Digital audio has a ceiling, 0 dB at full scale. When the signal tries to go higher, the samples stop at the ceiling and every peak becomes a flat plateau. You hear it as harsh distortion on loud words, drum hits or notes.

• In the waveform, look for peaks that run into the top and bottom edges and stay there. Zoom in with View ▸ Zoom In (=) and clipped waves look cut flat instead of round.
• Analyze ▸ Statistics… shows Possibly Clipped Samples: how many samples sit at full scale in the selection or the whole file.
• During playback, the clip light at the end of the level meter turns red at full scale.
• If the file was turned down after it clipped, the plateaus sit below the edges and the counter shows zero, but the flat tops are still visible when you zoom in.

How to repair clipping, step by step

The Clip Restoration window opens as soon as your file has loaded.

1. Click Open a clipped recording, or use File ▸ Open… (Ctrl+O), and choose your file.
2. Select the clipped passage, or leave nothing selected to repair the whole file.
3. Open Effects ▸ Noise Reduction ▸ Clip Restoration… if the window is not already open.
4. Pick a preset: Hard Digital Clipping for square, flat tops, or Soft / Analog Clipping for rounder tops from an overdriven preamp or tape.
5. Press Preview and compare with the original. The rebuilt peaks should sound cleaner, not louder.
6. Click OK, then open Analyze ▸ Statistics… and check that Peak Amplitude is below 0 dB.
7. If it is above, apply Effects ▸ Amplitude ▸ Normalize… and then save with File ▸ Save As… in the format you need.

Why the level goes down first

A rebuilt peak is taller than the plateau it replaces, so it needs room above the old ceiling. That is why Clip Restoration first lowers the selection by Input Attenuation, from -12 to 0 dB and -3 dB by default, and only then redraws the peaks. Each plateau then becomes a smooth curve that follows the slope of the good samples on either side.

• Input Attenuation: -3 dB suits light clipping. For heavy clipping, try -6 dB or more. The No Attenuation preset keeps the level, so the rebuilt peaks go over full scale until you lower them with Normalize.
• Clip Threshold (of peak), from 80 to 100%: how close to the loudest sample of the selection a sample must be to count as clipped. Around 99% fits hard clipping and 95% soft clipping. Since it is measured against the loudest sample, select passages that really clip.
• Minimum Clipped Run, from 2 to 32 samples: how many samples in a row must sit at that level. Higher values ignore short natural peaks; lower values catch brief clips.

What Clip Restoration can and cannot recover

It works best on short, occasional clipping: a few samples flattened on the loudest syllables or drum hits. There, the curve it draws is close to the wave that was lost.

It cannot bring back what was never recorded. When long stretches are flat, the curve is only an educated guess, and audio that was clipped and then compressed, limited or saved as MP3 no longer has clean flat tops to detect. It can soften the harshness, but recording again at a lower level is the only real fix.