Metering
Barometer provides ITU-R BS.1770-4 compliant loudness metering with true-peak detection, multiple time windows, and platform target references.
What is LUFS?
LUFS (Loudness Units Full Scale) is the international standard for measuring perceived loudness, defined by ITU-R BS.1770-4. Unlike simple peak or RMS meters, LUFS accounts for how human hearing perceives loudness across frequencies.
LUFS uses a K-weighting filter (boosting frequencies around 2–4 kHz where hearing is most sensitive) followed by a mean-square measurement. The result correlates closely with how loud something actually sounds, not just how loud the waveform measures.
Streaming platforms use LUFS for loudness normalization — if your master is louder than the platform's target, it gets turned down. If it's quieter, it may get turned up (platform dependent).
Measurement Modes
Momentary
400 ms windowUpdates every 100 ms using a 400 ms sliding window. Shows instantaneous loudness — useful for tracking peaks and finding the loudest moments in your material.
Short-Term
3 second windowSmooths out fast changes to show the perceived loudness of phrases and sections. Better for comparing the relative loudness of different parts of your track.
Integrated
Cumulative from startThe overall loudness from the moment you start playback (or last reset). This is the number streaming platforms use for normalization. Uses gating to ignore silence. Reset before each measurement pass.
Loudness Range (LRA)
Statistical rangeThe range between quiet and loud passages, measured in LU (Loudness Units). LRA 3–5 LU = heavily compressed, LRA 7–10 LU = typical pop/rock, LRA 10+ LU = wide dynamics (classical, film).
True Peak vs Sample Peak
Sample peak measures the highest digital sample value. But the actual analog waveform between samples can exceed the sample values — these are inter-sample peaks (ISPs).
True peak uses 4× oversampling to reconstruct the waveform between samples and catch ISPs. When lossy codecs (AAC, MP3, Ogg Vorbis) decode your audio, ISPs can become real peaks that clip the output. This is why streaming platforms require true-peak below -1 dBTP.
Barometer shows true-peak readings per ITU-R BS.1770 for both channels independently.
Platform Target Levels
Reference levels for major distribution platforms. These are normalization targets — the platform will adjust your audio to match.
| Platform | Target LUFS | True Peak | Notes |
|---|---|---|---|
| Spotify | -14 LUFS | -1 dBTP | Turns down louder masters; may turn up quieter ones |
| Apple Music | -16 LUFS | -1 dBTP | Sound Check enabled by default; AAC codec |
| YouTube | -14 LUFS | -1 dBTP | Turns down only; never turns up |
| Tidal | -14 LUFS | -1 dBTP | HiFi tier preserves original; normalization optional |
| Amazon Music | -14 LUFS | -2 dBTP | Stricter true-peak limit than most |
| Broadcast (EBU R128) | -23 LUFS | -1 dBTP | European broadcast standard; strict compliance |
| Broadcast (ATSC A/85) | -24 LUFS | -2 dBTP | US broadcast standard (CALM Act) |
| Podcast | -16 to -14 LUFS | -1 dBTP | Apple Podcasts recommends -16; Spotify -14 |
When in doubt, target -14 LUFS integrated with -1 dBTP true peak. This covers most platforms.