Sound level weighting There are two sets of units for expressing loudness, like volume, inside and outside the computer: sone (loudness unit, song), phon (loudness level unit, square), lkfs (used by itu International Telecommunications Union, using k weighting), lufs (used by ebu European Broadcasting Union. What does "sone" mean? Song means. is the unit of loudness. a unit of subjective loudness, equal to 40 phons (loudness unit, 1 phon equals 40 square meters). It is also related to frequency, defined as 1000hz, 40db, and the loudness of pure tone is 1sone. .
