What is in this article?:
Discussion and conclusions
Several studies have shown that the loudness “comfort range” for typical television listening is +2, -5dB20. Beyond this range, a viewer is likely to become annoyed, eventually reaching for the remote control to change volume (or worse, from the broadcaster’s point of view, to mute a commercial). Whether measured via the CBS or BS.1770 algorithms, the CBS loudness controller algorithm in Orban’s current products effectively controls subjective loudness to much better than this +2, -5dB window.
In the original version of this paper, we had assumed that results using BS.1770 metering would be more consistent if that algorithm employed gating to prevent unadorned dialog from reading low compared to music and dialog with substantial background music or effects. However, this did not prove to be true with the program material we used for testing; the results from the BS.1770-1 (ungated) and BS.1770-2 (gated) measurements were similar when measuring material that had been processed by the CBS loudness controller. It is likely that the loudness-controlled material seldom caused the gate to act. (The CBS algorithm does not need silence gating because it is a “short-term” loudness measurement that incorporates cascaded models of the “instantaneous” and “short-term” loudness time constants of human hearing21, which the BS.1770 algorithm does not.)
Controlling loudness to a standard such as BS.1770 says nothing about the subjective acceptability of the loudness controller’s action. We have found that a simple loudness controller that uses the inverse of the BS.1770 short-term meter’s output to control loudness by gain reduction can cause unnatural-sounding gain pumping of dialog when underscoring and effects appear under the dialog.
More complex automatic loudness controllers can produce all of the well-known artifacts of dynamics processing. Improperly designed multiband compressors can reduce dialog intelligibility22. This is why it is important to carefully assess the audio quality and side effects that an automatic loudness controller produces so that one can choose a device that controls loudness effectively without producing objectionable and unnatural artifacts that can fatigue audiences. Different loudness controllers do not provide equally good subjective results even if they produce identical measurements on a loudness meter.
Based on extensive experimentation with typical broadcast material, we believe that the CBS loudness meter locks onto dialog more effectively than does BS.1770, particularly when the dialog is accompanied by underscoring and/or effects. Unlike the BS.1770 meter, the CBS technology does not unnaturally penalize material having a low peak-to-RMS ratio, so it allows mixers and producers to freely use “artistic compression”23 and other well-established production techniques with the knowledge that such material will be neither too loud nor too quiet when compared to the surrounding program.