Weiss Enginering Ltd.
DAC501-4ch/DAC502-4ch
Outline of the algorithm
In the figure below the main functionality of the Weiss Loudness Normalization is outlined. The algorithm is
displayed as a simplified block diagram. It consists of four main processing blocks.
Figure 27: Block diagram of the Weiss Loudness Normalization
The first block Loudness Measurement uses a special procedure to evaluate the loudness envelope of the
signal within a very short time period. The characteristics of the human hearing-system are of course in-
cluded in this loudness measurement regarding the Recommendation BS1770 by the International Telecom-
munication Union.
With several signal processing tools this measurement will be adapted to become qualified for the use of
the normalization. In this way it is possible to create a very fast normalization but also save the important
dynamic content of the audio information to make the manipulation not disturbing.
The second block Clever-Mean-Evaluation with Time Sensitive Interpolation is the biggest part of the algo-
rithm. This block contains most of the sundry preparing steps to make the measured loudness envelope
suited to be used in the third block. Here the Normalization Gain is determined. Of course a special kind of
noise gating is used in this block. And finally the last block performs the adaptation of the audio signal to
create an output with constant loudness.
Level Definitions
By adjusting the Dynamic Level you can justify how intense the normalization should effect the audio signal.
To be able to use the plugin properly it is helpful to understand how the levels of the plugin effect the audio
signal. There are two main levels: the Dynamic Level and the Normalization Level. In the graphic on the
right the Normalization Level and the Dynamic Level are displayed.
The Normalization Level is fixed and is
used to ensure a proper overall maximum
output level.
If you change the Dynamic Level you
change the dynamic content of the audio.
So if you like to have more dynamics left
in your playback use a positive Dynamic
Level. The higher this level is the more
dynamic content is left in the output. The
lower (negative) this level is the less dy-
namics are left. More and more quite parts
of the original audio are amplified. More
and more loudness peaks are normalized.
Figure 28: Visualization of relation between dynamic level
and normalization level
All in all the whole playback becomes naturally louder when the Dynamic level is very low. Besides it is
important to emphasize that the effect of the Dynamics Adaption is depending on the musical content of the
actual playback. Some kinds of music have a very wide range of dynamics like a recording of an orchestra.
Other pieces are already very compressed concerning their dynamic range.
So it is clear that the effect of the Dynamics Adaption will sound different for different kinds of music. Also
the velocity of the loudness changes has an effect on the dynamic. And additionally the spectral content of
the music also effects how the output will sound in the end.
This illustrates the big challenge of a good sounding and fully automatic control of the dynamic range.
User Manual and
31
White Papers
