LUFS

LUFS (Loudness Units relative to Full Scale, sometimes called LKFS in the older ITU standard) is the measurement unit for integrated loudness — the perceived volume of audio content averaged over its duration, weighted by the K-frequency curve to match human hearing sensitivity. The development of LUFS-based standards solved a real broadcasting problem: commercials sounded much louder than programs even when peak levels matched, because peak amplitude poorly correlates with perceived loudness. The ITU-R BS.1770 standard defined the loudness measurement algorithm, and EBU R128 (Europe), ATSC A/85 (US TV), and platform-specific targets (Netflix -27 LUFS short-form, -27 LUFS Atmos integrated; Apple Music -16 LUFS; Spotify -14 LUFS; YouTube -14 LUFS; broadcast typically -23 LUFS integrated) define delivery targets. Modern audio meters display three measurements: Momentary (400ms sliding window, instantaneous reading), Short-term (3-second sliding window), and Integrated (full-program average from start to end). A typical mix is judged by Integrated LUFS versus the target, plus Loudness Range (LRA, the dynamic range) and True Peak (the actual maximum samples, not the integer-sample peaks). Mixers ensure their final masters land at platform targets, applying limiting and loudness adjustment where needed without overcompressing dialogue. Tools: iZotope Insight, Waves WLM, NUGEN VisLM, Pro Tools' built-in loudness meter. Reference: EBU R128, ITU-R BS.1770.