ABSTRACT
Loudness is a measure of the perceived magnitude of a sound. The basis of loudness measurement is primarily the “equal loudness” curve. The curves express constant loudness regarding constant tones, and this loudness is expressed in phon. Dolby’s method, which was mentioned earlier when discussing frequency weighting, claims to measure loudness. The recommendation “International Telecommunication Union (ITU)-R BS.1770 – Algorithms to measure audio programme loudness and true-peak audio level” has been a breakthrough for loudness quantification in the field of broadcast. It provides the possibility of defining a target level for the instantaneous loudness as well as of the full length of the program based on an adequate loudness measure. The ITU 1770 algorithm rather measures a long-term or continuous loudness and did not count for certain types of programs that may contain larger sequences with very low-level audio. The gating was introduced to prevent silent sequences from unintendedly lowering the loudness measure of the complete program.
