The term loudness (or sound power), with reference to the television environment, indicates a measure of the average volume level of the sound that the user perceives while listening to the entire duration of an advertising spot or program.
The precise measurement of the sound power of each event issued is extremely important in order to guarantee compliance with AGCOM resolution no. 132/06 / CSP of 12 July 2006, which establishes the prohibition on the diffusion of advertising messages and teleshopping with a sound power higher than that of ordinary programs.
On January 8, 2010, AGCOM 219/09 / CSP of 05/01/2010 entered into force, which in Annex A, entitled 'Technical parameters and methodologies for detecting the sound level of advertisements and teleshopping', provides the methodology for measuring sound power and the technical requirements of the relative measuring instruments, specifying, in particular, that:
loudness is measured according to ITU-R BS.1770 which defines the algorithms for measuring the audio signal in order to determine the loudness unit (LU) of the program and the peak level of the signal
the relative measuring instruments are those defined in the ITU-R BS.1771 Recommendation which defines the technical requirements for instruments compatible with the ITU-R BS.1770 standard
The International Telecommunication Union (ITU) in the ITU-R BS 1770 Recommendation specifies an algorithm to objectively determine the loudness of television programs, an intrinsically subjective magnitude in itself.
The most recent revision of the standard is 3 (ITU-R BS.1770-3), published in August 2012.
The loudness unit (LU) uses a scale of negative values, where the value 0 represents the maximum sound power value defined by the measurement system.
According to current legislation, the loudness unit (LU) for advertising blocks cannot exceed the value of -24LU.
To ensure that the audio signal output is compatible with the previous regulations, it is necessary to enter along the emission chain automated devices (ALC) for normalization to the legal values of the audio signal, capable of leveling the loudness of commercials and programs in the context range of allowed values.
The paradigm of the normalization of audio levels, based on the international standard ITU.R BS.1770, at all stages of the broadcast, production, distribution and transmission chain, is also the subject of the EBU (European Broadcasting Union) recommendation R128.
