One type of normalization is peak normalization, wherein the gain is changed to bring the highest
PCM sample value or analog signal peak to a given levelusually 0
dBFS, the loudest level allowed in a digital system. Since it searches only for the highest level, peak normalization alone does not account for the apparent loudness of the content. As such, peak normalization is generally used to change the volume in such a way to ensure optimal use of available dynamic range during the mastering stage of a
digital recording. When combined with compression/limiting, however, peak normalization becomes a feature that can provide a loudness advantage over non–peak-normalized material. This feature of digital recording systems, compression and limiting followed by peak normalization, enables contemporary trends in program loudness. ==Loudness normalization== Another type of normalization is based on a measure of loudness, wherein the gain is changed to bring the average loudness to a target level. This average may be approximate, such as a simple measurement of average power (e.g.
RMS), or more accurate, such as a measure that addresses human perception e.g. that defined by
EBU R128 and offered by
ReplayGain,
Sound Check and
GoldWave. For example,
YouTube's preferred loudness level is −14
LUFS, so if an audio program is analyzed to be −10 LUFS, YouTube will lower the loudness by 4 dB to bring it to the preferred level. Loudness normalization combats varying loudness when listening to multiple songs in a sequence. Before loudness normalization, one song in a playlist might be quieter than the rest, so the listener would have to turn a volume knob up to adjust the playback volume. Depending on the dynamic range of the content and the target level, loudness normalization can result in peaks that exceed the recording medium's limits, causing clipping. Software offering loudness normalization typically provides the option of
dynamic range compression to prevent
clipping when this happens. In this situation, signal-to-noise ratio and relative dynamics are altered.
Loudness standards Standardised normalized loudness levels vary by territory and application. • −24LUFS:
ATSC A/85 (US TV), NPRSS, and
PRX radio broadcast • −14LUFS:
Spotify,
YouTube and other
streaming platforms ==See also==