Metering

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).

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.