Increase Your IQ with Loudness Monitoring and Control from Snell
With inbuilt loudness measurement and control with IQ Modular from Snell you can rest assured that your HD transmissions contain high quality sound at the correct levels, without the need for additional equipment and expense. But why is this becoming so important, and how much do you know about the loudness standards and what the technical terms mean?
This month’s Increase Your IQ defines some of the loudness technical terms, and introduces the loudness monitoring and control capability available with IQ Modular from Snell.
Standards and Guidelines
ITU 1770-2 / EBU R128 defines the parameters to which audio loudness has to conform and considers the subjective nature of loudness measurement because most content has varying loudness levels, and traditional audio measurement tools such as peak level meters generally do not correlate to the overall “energy” of audio.
Figure 1: Loudness distribution for typical movie
EBU Tech 3341guidelines supplement EBU R128 standards with an industry recognized measure of loudness of any audio material. Units are described as LUFS (Loudness Unit Full Scale) or LU (Loudness Unit). LUFS can vary greatly over an entire program, as Figure 1 shows.
All of Snell’s IQUAV10 family of modules support loudness monitoring based on EBU Tech 3341 guidelines; with each module providing 2 independent measuring blocks, and up to 5 channels of processing (e.g. 5.1 with LFE omitted).
Four measures are available:
Momentary sample, the average loudness over the last 0.4 seconds.
Short term sample, the average loudness over the last 3 seconds.
Integrated: the average loudness since session reset. This is a gated value, where all values below -70LUFS are ignored.
LRA: This denotes the loudness range since session reset. This is a gated value also.
All of the IQUAV10 family of modules also boast loudness control tools based on industry standard algorithms from Linear Acoustic.
The algorithms offer:
Input AGC (Automatic Gain Control).
This is a front end gain control which ensures that subsequent processes are fed with the correct average levels.
Multiband AGC. A compressor allowing a medium ratio (3:1) adjustment of audio band. There are 5 default bands.
Multiband Limiters performs limiting on signals coming out of the multiband AGC.
Multiband EQ – frequency response tailoring – different per preset.
Final Stage: look ahead peak limiter and bass clipper adjustments for controlling residual peaks. This is the section that the output level (Master Level) operates.
See Your Loudness Values – Live!
And last, but by no means least Snell has also introduced an EBU R128 compliant loudness meter and monitoring GUI into its RollCall Control and Monitoring system. Giving you easy to read graphical displays for live loudness values, and a history log that can be scrolled back to analyze loudness levels from the start of recording. Start stop and reset controls are available and when partnered with the Snell RollMap network management software loudness logging and reports can be generated.
Using Snell’s IQ modules with built in loudness measurement and control, for either stereo or 5.1 surround sound audio, you can be sure that your HD transmissions contain high quality sound at the correct levels, without the need for additional equipment and expense…
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