Make your audiobook chapters pass ACX

Drop in your chapter files. Each one gets its levels, peaks, background noise and room tone fixed, is saved as a 192 kbps MP3, then gets measured again before you download it.

Checking your files is free.

Your audio is processed in this browser tab. It is never uploaded.

What gets fixed

  • Loudness set to about -20 dB RMS (ACX allows -23 to -18)
  • Peaks held below -3 dB
  • Background noise brought under -60 dB
  • 0.75 s of room tone at the start and 2.5 s at the end
  • Low rumble under 80 Hz removed
  • Saved as mono MP3, 192 kbps constant bit rate, 44.1 kHz

What it can't fix

ACX also has a person listen to your files. This tool doesn't remove mouth clicks, plosives, audible edits or misread lines, and it can't repair clipping or a recording that is mostly noise.

Listen to each fixed file before you upload it to ACX.