Audio Normalizer (Loudness)

Audio Normalizer measures how loud a file actually is and then corrects it to the loudness target you set, which is a different job from turning the gain up.

This is the EBU R128 loudnorm filter run twice over the same file. The first pass only measures, printing the integrated loudness, true peak and loudness range as JSON; the second applies one linear correction calculated from those exact figures. The two-pass route matters because a single-pass loudnorm adapts as it plays and can audibly pump, and when the measurement cannot be read back the tool falls back to that single dynamic pass and states in the result which of the two it used. The true-peak ceiling can also hold the correction short of your target rather than clip to reach it, so a file with little headroom may land above the number you asked for.

Both passes read the file from a virtual filesystem inside the page, so the audio is processed twice without being transmitted once. The loudness figures are shown to you and stored nowhere.

Matching a podcast episode to the loudness platforms expect, levelling a back catalogue recorded on different gear, preparing a mix so a streaming service does not turn it down on playback, and bringing an audiobook chapter into line with the rest.

Also known as: normalize audio · lufs normalizer · standardize song volume · audio normalizer (ebu r128 loudness)