Loudness, K-weighted, relative to full scale (LKFS) is a standard

loudness In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of ph ...

measurement unit used for

audio normalization Audio normalization is the application of a constant amount of gain to an audio recording to bring the amplitude to a target level (the norm). Because the same amount of gain is applied across the entire recording, the signal-to-noise ratio and ...

broadcast television systems Broadcast television systems (or terrestrial television systems outside the US and Canada) are the encoding or formatting systems for the transmission and reception of terrestrial television signals. Analog television systems were standardized by ...

and other

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) sy ...

and music streaming services. LKFS is standardized in ITU-R BS.1770. In March 2011, the International Telecommunication Union (

ITU The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Union ...

) introduced a loudness gate in the second revision of the recommendation, ITU-R BS.1770-2. In August 2012, the

released the third revision of this recommendation ITU-R BS.1770-3. In October 2015, the ITU released the fourth revision of this recommendation ITU-R BS.1770-4. Loudness units relative to full scale (LUFS) is a synonym for LKFS that was introduced in

EBU R 128 EBU R 128 is a recommendation for loudness normalisation and maximum level of audio signals. It is primarily followed during audio mixing of television and radio programmes and adopted by broadcasters to measure and control programme loudness. ...

. The EBU has suggested that the ITU should change the unit to LUFS, as LKFS does not comply with scientific naming conventions and is not in line with the standard set out in ISO 80000-8. Furthermore, they suggest the symbol for ''loudness level, k-weighted'' should be L_k, which would make L_k and LUFS equivalent when LUFS indicates the value of L_k with reference to digital full scale. LKFS and LUFS are identical in that they are both measured in absolute scale and both equal to one

decibel The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a ...

(dB). Loudness units (LU) is an additional unit used in EBU R128. It describes L_k without direct absolute reference and therefore describes loudness level differences.

References

{{Reflist Sound technology