DN (Dialog Normalization)

There is a wide difference in the apparent loudness between different TV programs’ audio content. In DTV, with by standard is AC-3 encoded, a program producer chooses one of 31 different dialog normalization (abbreviated DN or “Dialnorm”) values and this parameter is carried within the AC-3 datastream, where each step represents a 1dB change in level. The DN value is the difference in dB between the maximum level possible (0 dBFS) and the average loudness level of the program material. The smaller the difference between the maximum and program average levels, the lower the DN value is assigned. The lower the DN value, the lower the output volume of the AC-3 decoder is set in direct proportion, meaning that subjectively louder programs will be played back at lower volumes than those in which the average program level is less loud. This supposedly will obviate the user having to adjust the volume control between programs, once the audio listening level is set by the user.

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