Loudness and room-size was: TV-Mix for Theatre

[Frank Kruse]

Garret,
With all due respect, after reading your post about" calibrating my room" and that you are listening at 65spl and 79 blows your head off, you are over your heard when it comes to dealing with a show that will go into a theater. Do yourself and your client a favor and take one of your mixes or a portion of the show in question and play it back in a "Dub Stage" that is calibrated. It will be an eye (and ear) opener for you!

I thought of starting a new topic instead of hijacking the other.

Speaking of wich there definitely is some connection between roomsize and "felt" loudness. Example: When I listen to a master mixed on a "real" cinema dub-stage in my way smaller edit-room (5.1) wich is also calibrated to 85 even normal dialog almost blows my ears off. Allthough in theory 85 spl at my listening position is EXACTLY the same 85spl on the large scale cinema. When I edit I have found a good level translation at 79spl wich "feels" equivalent to the level I hear when I listen to the exact same sassion 1:1 on the dub-stage. I think Holman has mentioned this problem in one of his books. If I would work at 85spl in my small room and then walk to the dub-stage all my levels would be way to low for someone to have a preview of what I intendet the elements to be.

I always wondered if there are some white-papers that contain investigation on the relationship between the room-size and the "felt" loudness at a given spl level. It makes absolutely no sense to calibrate a 15squaremeter-room to 85dBSPL. The mix will definitely trun out too soft I think.


Of course it´s a totally different cup of tea when it come to mixing and not track-laying but still, there must be a physical reason for this. I doubt that it has to so with hearing psychology. Maybe something with the relation between the listener-speaker-distance in relation to the room-size wich leads to higher direct sound while a large scale stage induced more indirect sound at the listener´s position wich makes program played at 85 seem WAY louder in a small room that in the large one.

Any fundamental info on this problem would be of interest for me.

Frank.

[Richard Fairbanks]

I agree with you that the problem exists, and I too am interested in knowing why. I have some theories about it but no hard evidence. Maybe that should become a spare-time project? It seems related to the problems of measuring perceived loudness and the fallacy of relying on simple average power levels of dialog as a reliable volume indicator. I am sure the idea of direct vs. reflected power plays a fairly big role, along with frequency content.

[Frank Kruse]

With this in mind wouldn´t it be a bad advice to tell any sound editor to calibrtate to 85SPL? To MHO it makes absolutely no sense to calibrate an average size edit-suite to 85SPL. The track-lay will most likely be way to soft when the guy steps onto to "real" dubbing stage to have his elements mixed.
I think if you theatrical work where you don´t mix in your room but prepare sound elements that will be mixed on a large stage you are way better off to set the levels by listening to the dialogue track and set that to a decend but not to soft volume and then build your tracks from there in relation to the dialogue-track.
I think this would work way better than working to 85SPL, finding everything way too lound and then have a bad awakening when you step into the big studio and all your tracks are way too soft.

After having done a bunch of films in my room I found that 79SPL and less is a good start that translates very well and feels about the same like the exact same mix on the 85SPL large scale dub-stage. But 85SPL definitely doesn´t work and doesn´t translate when you don´t have a large room. Having said that I do not mix in my room. I prepare elements in mono, stereo, 5.0 and 5.1 that are then mixed on large scale dubstages.
I wonder if THX or Dolby have done some research on this topic especially while they "invented" pm3 and the like...

frank.

[dr sound]

Frank,
I've posted this before:
If your mixing in a small room try between 78 - 82 spl. The only way to know what is right for Editorial or Sound Design is to
experiment until you find the right level that translates to the target room or medium you are aiming for such as Theatrical mix on
"The Dub Stage" or Network TV mix. If you read my calibration thread and all the links you will see that advice.

[Craig F]

85 SPL is for a large room

My largest dub stage is 82
my smaller dub stages are 81
and my scoring stage is 79 on a TV curve

[Frank Kruse]

Wich in essence means: You shouldn´t mix in a small room for theatrical release even when it´s callibrated to 85. Luckily Dolby doesn´t licence tiny bedroom studios even when they run at 85spl :-D

I wanted to suggest the roomsize-loudness investigation to some students of audio engineering over here. They always look for topics for a thesis and have got the time and gear to do some measurements with a group of listeners.

frank.

[JKD99]

For comparison, we're at 84 here for LCR, and 81 each for surrounds. The stage is 9400 cu ft. Mixes/Dolby Digital printmasters we've done here sound just as intended at everything from the Laemmle (small cinema) to the Arclight Cinerama Dome (biiiiiiiig).

My 2¢ (C-weighted, slow)

[RenderBot]

Well we all know that the physical dimensions of a space are at work here. Within the dimensions, of course, we find direct sound and two type of reflcetive sound; early and late. Listeners in smaller spaces are subject to far more direct and early reflective sounds at a higher rate arrival than in a larger space correct? Therefore the reverberant levels are much higher and may even be additive depending on the frequencies in play.

In a larger space we would find that direct sounds would remain the same, whereas early and late reflections would arrive later and later depending on rom size. And in reciprocation to a small room, a larger room would have increasingly more late reflections as the size of the room increases. Therefore, sound waves have longer distances to travel, which equates to more time for sound to decay, causing a lower amplitude once it arrives at the listeners position.

In addition, The larger the room gets, so to does the diffuse and reverberant fields. A lot of sound mingles and is their levels are highly reduced in these fields. A small room has practically no reverberant field and a very small diffuse field.

Anyone familiar with the out of print "Tonmeister Technology" text? If not, it's worth checking out. There's also the most complete of all texts for the truly nerdy, the "Sound Engineers Handbook" by ballou. Handbook my a**! Damn thing should have a caution before lifting sign on it. However, it's got to be the most complete book on sound there is. If this book could fit in one's pocket, it would've been there when they built every great hall. It's sound in it's most fundamental form: numbers! But even if you're not a "hard engineer" (particularlly electrical for this text) it's still worth it. The concepts are all there, only expressed in numbers

Cheers,
RenderBot

[Frank Kruse]

hm. doesn´t the dolby-consultant re-allign the system every time you master a MOD? At least this is the case here. Before the MOD can be mastered the consultant checks all speaker-levels and the overall curve with an RTA. Do you master at the official levels or do US consultants accept levels that do not match the dolby levels?

frank.

[dcaudio]

I can think of a couple of theoretical reasons that a big room will sound louder than a small room.

I believe it would have to do with acoustics more than anything psychological.

For the sake of clarifying, lets assume that 85dbspl has been measured in both rooms at the same position. Lets assume all that all calibration signals and measuring equipment were identical.

If pink noise was used then the frequency response of both rooms should be somewhat close. Practically speaking the frequency response is probably not all that close. A typical bigger room will have more low end bass response than a typical smaller room due to the size of woofers moving air. So a typical bigger room will sound louder due to the increase in level at 20hz-50hz.

But, speaking theoretically a big room could have the same freq. response as a small room. If a fast Fourier transform (FFT) measurement technique or Maximum Length Sequence (MLS) measurement system is used freq, phase, and other things that measure the reproduction equipment you could obtain similarly calibrated systems.

So you could eliminate all the variables other than the size of the room. But the acoustics of the rooms would *obviously* be different. Early reflections from walls, ceilings, consoles, and other objects would be different. Although not necessarily, reverb time would most likely be different. Even if the RT60 is not different (say both are 1.5 secs) then the quality of the reverb would be different. The biggest difference would be that in the smaller room early reflections would come quicker than in the big room (kinda like setting a different pre-delay setting in a reverb unit). The larger room would have less early envelopment after transient material. The larger room's transients might stick out more than in a small room. The transients in a large room would be surrounded by quieter sounds than the small room. If that is the case I can see material that has unmasked transients sounding louder than material that has its transients masked by the reflections from the previous material (and the resulting decay of its own transient). Was that clearly written???

Practically, a typical small room will have a shorter RT60 than a larger room. This will mean that material played back in the small room will have less acoustical reverb added to the material than the same thing played back in a larger room. Therefore, the average level (which is more relevant to perceived loudness than anything else) in a small room will sound softer. But, this would mean when mixing in a small room your electrical levels would be louder than in a big room. This is the opposite of the effect that Frank said he was experiencing. Interesting and confusing. But maybe the big room and the small room have identical RT60 so that this is not an issue (or maybe the smaller room has a longer RT60 than the larger room)?

Sound Forge has a pink noise generator in which you could set the crest factor. I believe this was setting the amount of random material that peaks above the average noise. So watching different crest factors on a meter would give similar average readings but different peak readings depending on the integration time of the meter. Analogously two different rooms with different acoustics would give different perceived loudness.

Also, what about distance from the screen to the listening position. Can you assume that in a larger room there is a slightly longer time before the sound reaches the ears? I guess this could be adjusted for, but practically speaking is it? Assuming not, there would a longer time in a larger room for sounds associated with visuals. Say for instance that a door slams. You see the door slam and the sound happens simultaneously. But in a typical larger room first you would see door slam and you would hear it ever so slightly later. If this is happening the brain might interpret the more time associated with the whole event to be louder. But in two properly calibrated rooms (in this case audio and visual in perfect sync) this scenario would not come into play. Maybe a larger door, as seen on a larger screen, would sound louder psycho-acoustically???

Those were just a few shots in the dark, maybe a tidbit is relevant and accurate.

Cheerio.