Quote:
Originally Posted by
Edwin-S 
From what I understand "Dialnorm" stands for dialog normalization. I believe it is a system implemented by Dolby Labs to help even out audio levels so that dialogue levels will maintain consistency with peak audio levels in the rest of a particular soundtrack. I believe it was intended to prevent the problem of dialogue sounding too soft, followed by other audio being too loud. Instead of a person cranking up the audio for dialogue and then rushing to crank it down for audio at higher peak levels, Dialnorm essentially automates the process by creating an average audio level between the quietest section (dialogue) and the loudest peak level (everything else). That is how I understand it; however, if I have gotten it wrong someone can correct me.
OK, I'll correct you.

Dialnorm does stand for "dialog normalization", but what you're describing there isn't it. That description better fits "dynamic range compression", which, unlike dialnorm, can always be switched off. A lot of people confuse the two, and a lot of people who rail against the supposed evils of dialnorm are complaining about issues that have nothing to do with it.
Dialnorm is simply a setting within the DD bitstream that instructs the decoder to raise or lower the
total volume -- let me repeat that: the
TOTAL volume -- by a designated number of decibels. It does not, in any way, alter the relative levels of various elements within the mix. Peaks are not lowered, nor is the volume of dialog elevated with respect to other elements. The entire volume is either raised or lowered, and that's it.
Why would anyone want this setting? You already gave the answer:
Quote:
Originally Posted by
Edwin-S 
Also, it sounds like dialnorm was actually developed as a standard for broadcast audio. It sounds like it was intended to solve problems with audio level changes from broadcaster to broadcaster.
That's what dialnorm was designed for, and it's for this reason that some sound designers (notably Larry Blake, who oversees all of Steven Soderbergh's films) have argued that dialnorm should be set to neutral on media like DVD, where the purpose for which the setting was created simply doesn't apply. In practice, though, most DD tracks have a dialnorm setting that is typically the default on various Dolby encoders, which is technically known as -27DBFS (= decibels below full scale). This results in telling the decoder to lower the playback volume by 4db. With very few exceptions, most DD tracks I check have this setting.
Is dialnorm defeatable? Yes and no. Denon used to offer a few receivers where you could switch off dialnorm, but that put them out of compliance with the DD spec and raised a question of whether they could carry the Dolby logo. So that feature disappeared. But dialnorm has always been defeatable by a feature available on all receivers and pre-pros. It's generally known as the volume knob.

(Note: Some people have tried, from time to time, to construct elaborate pseudo-scientific-sounding arguments about how a volume reduction instituted by dialnorm actually introduces distortion in the digital decoding because of . . . well, it never does make much sense. I sometimes listen politely, then move on with the business of life.)