This is part 5 after the installation, he takes measurements and if I remember correctly just about 50db iwhich is pretty decent.
56 dB according to the video, but the test procedure is not correct, as Greg pointed out: you can't measure isolation with pink noise at constant level, and not very loud to start with! They used only 90 dBC inside the room, which is about one hundred TIMES quieter than a typical practice sessions would be. The average rock band with acoustic drums and bass would EASILY be over 110 dBC, and perhaps even heading for 120 dBC. That's a HUGE difference in level: two orders of magnitude and perhaps three. So the MSM resonance of the room as not fully triggered to the same extent that it would be for a typical rock band rehearsal, and the sound they used for the test was not suitable, nor was the speaker.
Yes this is because I am using steel framing. When using steel framing (and working with a concrete outer leaf as in my case) first the ceiling is mounted using a system whereby the framing is suspended from the original concrete ceiling by thin metal bars (I have added an image). These bars have "silencers" on them that reduce structural noise and flanking that may occur via the bars. Then the steel framing for the walls goes between that ceiling and the floor so that the inner leaf is completely decoupled from the outer leaf. Have you heard of this system?
You are mounting your ceiling on resilient mounts, which suffer from the same general drawbacks as Resilient channel, or hat channel on RSIC clips. There's a limit to how much isolation you can achieve like that, which is roughly 16 dB better than a standard wall.. or roughly 56 dB...
:)
What do you recommend here on the forum with regards to metal framing?
Use STRUCTURAL metal framing, not the typical thin, flimsy stuff meant for partition walls...
I attached another image with different assemblies and their STCs
Forget STC. t is no use at all for telling you how well your studio will be isolated. STC was never meant to measure such things. Here's an excerpt from the actual ASTM test procedure (E413) that explains the use of STC.
“These single-number ratings correlate in a general way with subjective impressions of sound transmission for speech, radio, television and similar sources of noise in offices and buildings. This classification method
is not appropriate for sound sources with spectra significantly different from those sources listed above. Such sources include machinery, industrial processes, bowling alleys, power transformers,
musical instruments, many music systems and transportation noises such as motor vehicles, aircraft and trains. For these sources, accurate assessment of sound transmission requires a detailed analysis in frequency bands.”
It's a common misconception that you can use STC ratings to decide if a particular wall, window, door, or building material will be of any use in a studio. As you can see above, in the statement from the people who designed the STC rating system and the method for calculating it, STC is simply not applicable.
Here's how it works:
To determine the STC rating for a wall, door, window, or whatever, you start by measuring the actual transmission loss at 16 specific frequencies between 125 Hz and 4kHz. You do not measure anything above or below that range, and you do not measure anything in between those 16 points. Just those 16, and nothing else. Then you plot those 16 points on a graph, and do some fudging and nudging with the numbers and the curve, until it fits in below one of the standard STC curves. Then you read off the number of that specific curve, and that number is your STC rating. There is no relationship to real-world decibels: it is just the index number of the reference curve that is closest to your curve.
When you measure the isolation of a studio wall, you want to be sure that it is isolating ALL frequencies, across the entire spectrum from 20 Hz up to 20,000 Hz, not just 16 specific points that somebody chose 50 years ago, because he thought they were a good representation of human speech. STC does not take into account the bottom two and a half octaves of the musical spectrum (nothing below 125Hz), nor does it take into account the top two and a quarter octaves (nothing above 4k). Of the ten octaves that our hearing range covers, STC ignores five of them (or nearly five). So STC tells you nothing useful about how well a wall, door or window will work in a studio. The ONLY way to determine that, is by look at the Transmission Loss curve for it, or by estimating with a sound level meter set to "C" weighting (or even "Z"), and slow response, then measuring the levels on each side. That will give you a true indication of the number of decibels that the wall/door/window is blocking, across the full audible range.
Consider this: It is quite possible to have a door rated at STC-30 that does not provide even 20 decibels of actual isolation, and I can build you a wall rated at STC-20 that provides much better than 30 dB of isolation. There simply is no relationship between STC rating and the ability of a barrier to stop full-spectrum sound, such as music. STC was never designed for that, and cannot be used for that.
Then there's the issue of installation. You can buy a door that really does provide 40 dB of isolation, but unless you install it correctly, it will not provide that level! If you install it in a wall that provides only 20 dB, then the total isolation of that wall+door is 20 dB: isolation is only as good as the worst part. Even if you put a door rated at 90 dB in that wall, it would STILL only give you 20 dB. The total is only as good as the weakest part of the system.
So forget STC as a useful indicator, and just use the actual TL graphs to judge if a wall, door, window, floor, roof, or whatever will meet your needs.
The 3 leaf system in this image is inferior to the 2 leaf system in this image but this is not the same as having the 2 leaf system AND having an additional leaf outside which is what I will have.
Three-leaf is three-leaf, no matter HOW you build it. It is still a resonant MSMSM system. It doesn't matter if you start at the outside, or the inside, or the middle: it is still three leaf. If you stand inside the completed room, and there are three "leaves" between you and the outside word, then you have a 3-leaf system, and it is identical to the situation in the diagram yo posted.
The way I saw it when planning this is that having the 2 leaf system AND then having another leaf can only improve isolation.
No it cannot. IT can only make it WORSE for low frequencies. It might be better for mids and highs, but they don't matter so much anyway, but it WILL be worse for lows, all other factors being equal.
You can either do the walls first but then they need to be fastened to the outer leaf top and bottom.
Why???? What reasons would you have for needing to fasten walls to something else before you put a roof on? Please look closely at this photo:
Image not preserved: timber-shed-SML-ENH.jpg
It shows a structure built with four walls, then the roof was put on top. Are you saying that they should have attached this building to something else, to prevent it from falling over? Are you saying that it needs be fastened to something else, to keep it upright and stable? I find it hard to understand that logic. That shed looks pretty firm and stable to me.
Your inner-leaf room should be built EXACTLY like that photo: four walls with a roof on top. You do NOT need to attach the walls to anything else if you build it correctly. It will stand up all by itself, just like any other four-wall-plus-roof structure stands up.
You must do the ceiling first and erect the walls to that ceiling.
So you are saying that the guy who built this shed in the photo above, first put up the roof, making it float in mid air, all by itself, and then he built the walls, hanging them form the roof?
8) :D I don't think he built it like that! I rather think he built the walls first, then put the roof on top of them...
If you or anyone else has another way, I sure as hell would like to know
Well, I actually have built sheds, so I know that it DOES work rather well, when you build the walls first, then put the roof on. I have never had any trouble doing that. But I would love to hear how your system works! HOw do you make the roof levitate in the air by itself, until you can build the walls under it? That's some special kind of magic you have...
:)
This is the way it is done here.
Video please! I REALLY want to see how you guys make your roof float in the air every time you build a shed, house, office school, mall, hanger, shop....
:)
It is how a room in a room is built with steel framing in my country
Then I can confidently say that your studios in France do not get excellent isolation... You can ONLY get excellent isolation when the inner "room" is completely decoupled from the outer "room", with no mechanical connections at all between them: Not even resilient ones. When you have a resilient connection, that works IN PARALLEL with the air resilience, so you have thus REDUCED the resilience, and placed a limit on the total isolation. It can now NEVER be as good as if the only resilience was air itself. You force the MSM resonance to a higher frequency, and you reduce isolation. Simple physics.
I know that this system is is also used here because several soundproofing companies use this method
I'm sure they do! And make a FORTUNE from doing that... from looking at the video, I kept on thinking: "WOW! they must have a lot of money! That's a really expensive way of doing things!". Not to mention complicated. I don't know if you speak speak Spanish, but one of the final comments on Part 3 roughly translates as "Doing the ceiling this way was a right royal pain in the ass!" I agree. It certainly was. And it cost a LOT of money. And was not necessary. It could have been done much cheaper, more simply, faster, and better.
Yes but the problem is not in the isolation they provide but how the system is mounted/decoupled.
Sorry, but that's the exact same thing! It's sort of like you saying: "Yes but the problem is not in the water they provide but how wet and heavy the water is". Ummmm... that's exactly the same! They WAY you mount and decouple the ceiling (or the walls, or anything else) determines HOW it will isolate. Period. End of story. If you do not fully decouple the inner-leaf from the outer leaf, then you have placed a limit on how much isolation you can get. There are studies and white papers that clearly demonstrate this. With a resilient mounted system, you are limited to about 16 dB improvement over the original fully-coupled system. Laws of physics. So the METHOD that they used in that video means that they CANNOT get more an 16 dB improvement over doing the exact same thing bit WITHOUT the resilient mounts In other words, using solid, hard, rigid mounts. On the other hand, if you fully decouple your inner-room, then your maximum possible isolation is limited only by the concrete slab, and the resilience of air itself. So likely around 70 dB or so, for a typical home studio. Vs. the 56 dB they THINK they got here, but I'd be surprised if the REAL isolation is much above 50, to be honest, because they did not test it correctly.
He should have been playing a bunch of music with low end
:thu: And playing LIVE, not on speakers. There's a difference between sound PRESSURE and sound POWER. A small speaker stands no chance of putting out the same sound power as a full drum kit can.
I'm not saying this is the worst, but for the space it takes up, you could build it better.
I agree! And cheaper, too. Part of that system uses a sticky-backed MLV sheet, which they complain about greatly in the video: trying to get that in place on the ceiling was a major issue, and you can see in several places they didn't manage to do a good job: there are gaps between the MLV sheets... Not a good system. Complex, expensive, slow, and not as effective as a normal "room-in-a-room".
I have no doubt that the system works! I'm sure it does. There's huge amounts of mass in there. It just doesn't work as well as it could, if done correctly.
Build it out of wood.
:thu: Absolutely. Or use structural steel framing, not light-weight steel framing.
Build your walls (just anchor them to one another), then place a ceiling on top.
:thu: Yup!
- Stuart -