Hello all, been lurking for quite a while, well, ever since my employer asked me to help design a podcast studio. Predictably, my first post is a question. (hehe)
At any rate, here is the proposed layout of the studio:
Here it is as a 3D rendering:
A little more information you might be interested in is that we're talking about 5/8" sheetrock on med. 2.5" steel stud, insulated walls. The main and producers glass is to be double glazed (as thick as the wall) 1/4" one side and the other 1/4" laminated.
All walls are all to the upper deck and have an average STC of 48 (current door is a solid wood core, mediocre sealed at the moment)
I think you'll be able to spot the trouble right away; he is sold on having full light doors to both the producers room as well as into the studio.
Now, knowing the inherent weak link that is, I had an idea to mitigate it and wanted to get some feedback.
Here are the existing doors in question:
Here is my idea for custom built, full light doors of more than an STC of 32:
Do you think this will give me anything close to what I'm after?
Studio door questions
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Soundman2020
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Re: Studio door questions
Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things! 
That said, there's a number of issues with the numbers you quote that make it unclear what the current situation is, and what you want it to be.
First: "All walls are all to the upper deck and have an average STC of 48 (current door is a solid wood core, mediocre sealed at the moment)". How did you determine that the current rating is STC-48? Did you do the full set of tests at all of the STC suite of frequency bands, then do the math to determine that the wall is rated at STC-48? Or did you assume that it is rated at STC-48 from seeing the theoretical ratings of similar walls? Or did the contractor who built it tell you that he measured it and found it to be rated at STC-48? Or something else? STC-48 is such a specific rating: it is important to know how this was determined.
2) Is that enough? You didn't mention what the design goal is for TL (in decibels, not STC- ratings), nor what types of sounds need to be excluded from the studio (TL in each frequency band), so it would be necessary to know if the current STC-48 measurement of your walls is sufficient, or if you need more, and if so, how much more?
3)
4)
5)
There's your problem. The door is a major issue, regardless of the glass. Even if you put 1" of triple-laminated glass in there, with both PVB0c being acoustic, you'd still never get more than 33 dB out of it. you can't fool the laws of physics.
6) "Here is my idea for custom built, full light doors of more than an STC of 32:" Nope. Not going to happen. The isolation from the two-leaf MSM glass system would reduce the overall TL of the door. The MSM resonant frequency for the glass configuration you propose would be 134 Hz, so the isolation would be poor below about 400 Hz. Somewhere around 11 dB at resonance. I would estimate that you'd get no more than about STC-27 from such a door. A bit worse than for a solid wood door with no window.
It would make more sense to do the window with a single pane of glass that has roughly the same surface density as that of the wood: you'd need 1/2" laminated glass, made up as 1/4"+APVB+1/4". That would give you roughly the same performance for the entire door, of around STC-31, assuming that you do excellent seals and mount it perfectly.
7) "Do you think this will give me anything close to what I'm after?". In a word: no. Not enough mass, no damping, reduced isolation at resonance, which is at a high frequency anyway, due to the thin light-weight glass and tiny air gap. That resonance is well within the STC data points, so it would go into your calculations, and pull down the over rating.
8 ) One other question: Why are you going to all the trouble to measure and calculate everything in STC. which is such a complicated system anyway, and isn't really applicable to studios either? If you are making all those measurements just to come up with the STC number, then why not make a few more and just plot the entire TL instead? Far more useful.
9) You never stated it in your post, so maybe you could clarify exactly what level of isolation you are looking for in the studio: How many dB of TL do you want?
10) Regardless of what you do with the walls and doors, the single largest flanking path in most offices is the HVAC system, but you made no mention of that, which leads me to think that it has been overlooked. What are your plans for isolating the HVAC system to the same level as the walls, ceiling, floor, and doors?
11) No mention was made of the NR or NC curve that you guys are aiming for: It doesn't matter how good your STC rating is, if the overall NR or NC is still too high to be usable. What NR (or NC) curve are you aiming for?
Lot's of questions up in the air here...
I would suggest that you tell your boss that he's never going to get usable isolation unless he approaches this project properly, and has the entire room properly designed and built for this specific purpose, taking into account all of the above, and aiming for a specific agree-on isolation goal and noise goal.
- Stuart -
That said, there's a number of issues with the numbers you quote that make it unclear what the current situation is, and what you want it to be.
First: "All walls are all to the upper deck and have an average STC of 48 (current door is a solid wood core, mediocre sealed at the moment)". How did you determine that the current rating is STC-48? Did you do the full set of tests at all of the STC suite of frequency bands, then do the math to determine that the wall is rated at STC-48? Or did you assume that it is rated at STC-48 from seeing the theoretical ratings of similar walls? Or did the contractor who built it tell you that he measured it and found it to be rated at STC-48? Or something else? STC-48 is such a specific rating: it is important to know how this was determined.
2) Is that enough? You didn't mention what the design goal is for TL (in decibels, not STC- ratings), nor what types of sounds need to be excluded from the studio (TL in each frequency band), so it would be necessary to know if the current STC-48 measurement of your walls is sufficient, or if you need more, and if so, how much more?
3)
. Based on that and the images you provided, it seems there is no decoupling in those walls, so they are basically single-leaf walls, and subject mostly to Mass Law for isolation (Yeah, technically they are fully-coupled 2-leaf walls, but in that configuration they will act more like single leaf walls). The question is simply: Why? This is a studio that needs good sound isolation, so why was no effort made to isolate it? What you describe is unlikely to be giving you STC-48 in any case: more like STC-40, give or take a couple of points. I assume that you used mineral wool insulation, such as Rockwool? Is it too late to take the walls apart and fix them to get good isolation?...we're talking about 5/8" sheetrock on med. 2.5" steel stud, insulated walls....
4)
That's not very thick. Not too much isolation going on from thin glass like that. But for what is basically a single-leaf wall, that is probably fine. That will get you roughly STC-38 to STC-42, so roughly the same as the walls. But it won't be STC-48.The main and producers glass is to be double glazed (as thick as the wall) 1/4" one side and the other 1/4" laminated.
5)
. Yes: that entire door is the trouble, bot just the glass. There0s nowhere near enough mass in that door to get good isolation, and it does not look there there are three sets of full perimeter seals on it either! A door like that will get you maybe STC-30-something on a good day, if that. 1-1/2" of solid wood is going to get you overall TL of around 34 dB, maximum, no matter what you do with the glass or seals. That's the Mass Law limit for an inch and a half of typical wood. So assuming that door was built perfectly, with perfect triple seals, in perfect frames, it would maybe get you 34 dB of TL. In the real world, more like 31, with luck. If the seals are poor, knock another couple off. If the latch hardware goes all the way through the door (ie,l there's a hole drilled in it), then knock off yet another 2 or 3.I think you'll be able to spot the trouble right away;
There's your problem. The door is a major issue, regardless of the glass. Even if you put 1" of triple-laminated glass in there, with both PVB0c being acoustic, you'd still never get more than 33 dB out of it. you can't fool the laws of physics.
6) "Here is my idea for custom built, full light doors of more than an STC of 32:" Nope. Not going to happen. The isolation from the two-leaf MSM glass system would reduce the overall TL of the door. The MSM resonant frequency for the glass configuration you propose would be 134 Hz, so the isolation would be poor below about 400 Hz. Somewhere around 11 dB at resonance. I would estimate that you'd get no more than about STC-27 from such a door. A bit worse than for a solid wood door with no window.
It would make more sense to do the window with a single pane of glass that has roughly the same surface density as that of the wood: you'd need 1/2" laminated glass, made up as 1/4"+APVB+1/4". That would give you roughly the same performance for the entire door, of around STC-31, assuming that you do excellent seals and mount it perfectly.
7) "Do you think this will give me anything close to what I'm after?". In a word: no. Not enough mass, no damping, reduced isolation at resonance, which is at a high frequency anyway, due to the thin light-weight glass and tiny air gap. That resonance is well within the STC data points, so it would go into your calculations, and pull down the over rating.
8 ) One other question: Why are you going to all the trouble to measure and calculate everything in STC. which is such a complicated system anyway, and isn't really applicable to studios either? If you are making all those measurements just to come up with the STC number, then why not make a few more and just plot the entire TL instead? Far more useful.
9) You never stated it in your post, so maybe you could clarify exactly what level of isolation you are looking for in the studio: How many dB of TL do you want?
10) Regardless of what you do with the walls and doors, the single largest flanking path in most offices is the HVAC system, but you made no mention of that, which leads me to think that it has been overlooked. What are your plans for isolating the HVAC system to the same level as the walls, ceiling, floor, and doors?
11) No mention was made of the NR or NC curve that you guys are aiming for: It doesn't matter how good your STC rating is, if the overall NR or NC is still too high to be usable. What NR (or NC) curve are you aiming for?
Lot's of questions up in the air here...
I would suggest that you tell your boss that he's never going to get usable isolation unless he approaches this project properly, and has the entire room properly designed and built for this specific purpose, taking into account all of the above, and aiming for a specific agree-on isolation goal and noise goal.
- Stuart -