How it works
The processing chain, step by step
No black box. These are the exact stages every file goes through, in order, and how the result is verified.
Measure the original
We decode your file and measure integrated loudness, loudness range and true peak with the ITU-R BS.1770 / EBU R128 method, plus RMS level, sample peak and the noise floor (the lowest RMS of a 400 ms window, measured the way the ACX Check plugin does). These numbers appear in the "before" column of your report.
Bring it to a working level
The file is temporarily set to -24 LUFS so the clean-up stages treat a quiet phone recording and a hot studio file the same way.
Clean up (each stage optional)
Rumble filter: 80 Hz high-pass. Noise reduction: spectral noise reduction that tracks the noise profile over time. De-esser: reduces harsh sibilance. Leveler: a slow dynamic normalizer that evens out speakers and segments while leaving pauses alone, followed by gentle 2.5:1 compression. Presets choose sensible defaults; you can switch any stage off.
Set the loudness
We measure the cleaned signal and apply the exact gain that reaches the target. Podcast, video and broadcast presets target integrated loudness in LUFS; the ACX preset targets RMS level, because that is what ACX measures.
Limit true peaks
A lookahead limiter runs at four times the sample rate, which catches the inter-sample peaks that ordinary sample-peak limiters miss. For MP3 and AAC we leave an extra 1 dB of headroom because lossy encoding can raise peaks.
Encode and verify
The master is encoded to your format and measured again. If the delivered file misses the loudness target or exceeds the peak ceiling, we correct the gain or ceiling and render again, up to three times. The report shows the final measurements, not the intended ones.
What we do not do: we do not use generative AI, change what is said, add music or effects, or keep your audio for any other purpose. The processing is standard digital signal processing, and your files are deleted after 7 days.
Measurement details
| Value | How it is measured |
|---|---|
| Integrated loudness (LUFS) | ITU-R BS.1770 K-weighted, gated loudness over the whole file (absolute gate -70 LUFS, relative gate -10 LU) |
| True peak (dBTP) | Peak of the 4x-oversampled signal, per ITU-R BS.1770 |
| Loudness range (LU) | EBU Tech 3342 distribution of short-term loudness (10th to 95th percentile) |
| RMS level (dB) | Root-mean-square level of the whole file, as used by ACX |
| Noise floor (dB) | Lowest RMS of a 400 ms window evaluated every 100 ms (the ACX Check method), ignoring absolute digital silence |
Want to see these values for a file right now? Use the free LUFS meter or the ACX check; both run in your browser.
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