The ITU loudness standard uses K-weighting with a 4 dB high-frequency head boost.

Evidence

The RLB curve provides the basis for “K” weighing used in ITU R-REC-BS.1770-5 (2023), which adds a 4 dB boost above about 1 kHz to accommodate the acoustical gain added by a spherical head. This international standard is aimed the radio and TV broadcast industries and embraces reproduction in mono, stereo and multichannel formats. Measurements using this standard are called LKFS, meaning Loudness K-weighted Full Scale. It is extensively used in the professional audio recording and streaming industries. Users set a reference level they wish to maintain, and monitor progress using LUFS, Loudness Units Full Scale, to follow real-time loudness levels compared to that reference. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1178

Categorization

• DEFINE: Clarifies the RLB/K-weighting origin and defines LKFS and LUFS metrics underpinning broadcast loudness normalization.