Regarding the hearing damage aspect, I think there needs to be better data and laws regarding damage done by transient sounds. Most of the Health & Safety laws around the world are related to more continuous, industrial noise. Depending on where you are in the world, this typically means anything continuous over 85dBA is considered bad. What we experience in film isn't continuous, but can have very sudden dynamics and that's where the danger lies I think.
Although I'm a sound engineer not a medical expert, AFAIK the ear has two coping mechanisms (chemical and muscular) to fend off loud noise, both of which cope to some extent when noise builds up gradually, but are defeated by a instantaneous blast of 110dBC coming out of 40dBC "silence".
About 15 (OK maybe 20...
) years ago I had to wear a noise dosimeter while mixing a loud action movie. We were typically working 12 hours a day. Often sitting on scenes approaching 110dBC. From a H&S perspective, they would say "no damage was done" because it's below the
averaged action level, by law. I promise you, damage is done.
Anyway, regarding reference level.... I know I keep banging on about it on ASR but I just don't believe there is any such thing in home entertainment mixes. While THX may *say* reference level is -20dBFS=85dBC, that's completely irrelevant if the home ent mixes aren't done to the same reference to begin with. Which for the most part, they aren't. I don't recall ever being asked to do a home entertainment mix to THX reference. There are probably a few out there.
They're basically saying their reference is the same as Dolby Theatrical reference, hence
if someone put the cinema mix out for consumer use, and you set the AVR to 0, it would be the same level as in a cinema with the cinema processor set to "85" or "Fader 7" in Dolby speak. While that's commendable to some extent, almost no one is putting out content like that any more. As much as it's a shame for Home Theater owners, a (cinema) wide dynamic mix is not going to be acceptable for the majority people at home; complaints like "I couldn't hear the dialog" and "I had to reach for the volume control" being common with such material. We have no delivery method where the end user can select a different audio track based on their dynamics preferences. As such, the home ent mix is usually some sort of compromise for best fit.
Netflix give public visibility of their home entertainment spec, which is in the same ballpark as most others, but also quite clearly written compared to most tech specs
:
https://partnerhelp.netflixstudios....-Atmos-Home-Mix-Deliverable-Requirements-v2-1
Theirs is a dual pronged attack, a mix level of 79 or 82 (recommended, I sometimes use as low as 77 depending on content). BUT having done the mix if you're off target loudness of -27LKFS dialog gated, the whole mix needs to be turned up or down to hit target. At which point, your "reference" level changes by an equal and opposite amount. Typically once you're used to a certain spec you can get to within about a dB of it by ear, but even so, you can see the range of "reference" for Netflix alone is going to be 77 to 83 ish.
I will say that sometimes there's a separate Blu-Ray mix, but many of the big players now use just two mixes; a Theatrical mix for cinema release and a nearfield mix for everything else (Disc, VOD, broadcast)
Lastly, just to be clear, the fact we call reference "85dB" or whatever is a totally arbitrary number to facilitate replay gain alignment / unification. Nothing about a mix is anchored to a reference SPL. We don't have any meters that show us this level while we mix.
This was all a very long winded way of saying, if you're hitting 105dBC/channel with a modern HE mix, the chances are you're listening a lot louder than it was mixed.
