Any recommendations on the best way to isolate the ceiling a reasonable degree? Goal: footsteps and upstairs noise not transmitting at all;
Structure-borne noise is a nightmare. Once the vibration (noise) of those footsteps get into the building structure (floor deck, ==> joists, ==> walls, =>>....) it is everywhere, and stopping it is a huge pain. It is far better to prevent it from ever getting into the structure at all. I would suggest investing in some nice thick good quality carpet, with a nice thick acoustic underlay, to go on the floor upstairs. That will greatly simplify your job, since it will largely prevent the sound of those footfalls from making it into the structure.
For the glass stairway door, we decided on the sliding doors ... as the 42 STC should be enough for our purposes of reducing sound between living area upstairs and production room downstairs.
It's a pity you took that decision without checking back with the forum. And it's also a pity that you chose a single door based on "STC", which is a pretty useless method for measuring STUDIO isolation. It's fine for typical house, office, school, shop, etc. isolation, but no use at all for measuring studio isolation. Here's why:
STC was never meant to measure such things! That was never its purpose. Here's an excerpt from the actual ASTM test procedure (E413) that explains what STC is, and what it should be used for:
“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 very 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.
on the other hand, when you measure the isolation of a studio window, 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.
That's why I say it is unfortunate that you made decisions on purchasing expensive products based on rating systems that are not applicable to your case, and when you don't even have an actual design for your isolation system.
Sorry to be harsh and "in your face", but what you are doing right now is pretty much the same as a car mechanic trying to do brain surgery on himself: You are both sort of fiddling and poking around without having any idea what you are doing, and are probably causing way more harm than good. And in both cases, the outcome is very unlikely to be successful... They only real difference is that the mechanic will probably kill himself in the process, whereas you will merely wast a lot of time and money...
![Smile :)](./images/smilies/icon_smile.gif)
(However, if you don't do the structural calculations for your studio build, you might end up killing yourself as well, when the ceiling collapses on your head....
OK, now that I have your attention, I'd really suggest that you should stop right where you are in the process, right now, and not do anything else until you actually have a plan in place. A real, complete, details plan, not just for the isolation, but for the entire studio, including isolation, structures, HVAC, layout, geometry, treatment, tuning, electrical, etc. Every single aspect of your entire build should be planned in full detail, and carefully calculated to ensure that it will actually do the job you are desperately hoping and wishing it will do, but right now actually have no idea if it will do or not.
In my first reply to your thread last year, I did suggest this. You didn't take that advice, and that's fine! Nobody is forcing you to take it! But if you come to a forum that hands out professional advice for free, and then choose not to take it, we get back to the situation of the mechanic who actually went to the brain surgeon, who told him what the correct procedure was for diagnosing his illness, but the mechanic chose to ignore that advice and instead attack his own head with a pneumatic drill and a hand saw...
The sprinkler system must remain in place,
That's a major complication if you want high isolation. You might not realize it yet, but that's a big deal.
music noise of most instruments inaudible upstairs, with louder instruments like drums as slight as possible.
Drums commonly out out around 110 - 115 dBC. Most people would call it "silent" if the ambient noise level were less than about 40 dB. You would need 70 dB of isolation to get that. A typical house wall provides around 30 dB of isolation. The decibel scale is logarithmic, not linear, so each time you go up ten points you are actual talking about ten TIMES the intensity. In other words, to increase isolation from the typical 30 dB of a house wall to 40 dB, you need to block ten times as much sound. Going from 40 to 50 is another step of "ten times", which implies that going from 30 to 50 is one hundred time as much. So from 30 to 60 is one thousand times as much, and from 30 to 70 is ten thousand times as much. In simple terms, what you need to do is to block about ten thousand times more sound intensity than you are blocking right now.
That should put things in perspective for you, I hope.
Fully isolating a drum kit in a typical house is a major, huge, big deal. Even isolating it partially, so it is only vaguely audible, is still a big deal. Even increasing isolation by ten points is not simple. To put that in perspective: if you were to DOUBLE the total amount of mass of that floor above you, it would increase the isolation by around 5 to 6 dB. If you were then to double it AGAIN (four times the original mass you would get another increase of 5 to 6 dB, for a total of around 10 dB. And your floor would probably collapse, from the severe structural overload.
By adding mass alone, you are fighting a loosing battle, because the principle of physics known as "mass law" is not your friend, and is a lousy way to isolate. As I mentioned in my first response to your initial post, what you need is "a properly designed and built 2-leaf isolation system", but there's no sign of that in what you are doing right now, so your chances of success are pretty low.
Based on your comments, you have a few bits and pieces of the plan in mind, sort of, vaguely, but you do not have an actual plan, and that's a problem.
So the very best I can do for you is to NOT answer your questions, since you are not asking the right questions, and answering them would only lead you further astray. The best advice I can give you is to stop where you are, and start working on your plan. Your actual, detailed, physical plan that shows all parts of your studio, with all materials, dimensions, and calculations completed. Then only when you have all that in order, only then should you carry on building. Trying to build a studio without a plan, is like trying to go on vacation without a map, an without even knowing if you are going to drive, fly, walk, sail or swim to get there!
the largest soffit, however, has all kinds of pipes and conduits, an old duct system, etc., which we have to deal with by either removing or capping and sealing, and we plan to install new HVAC (Daikin cassette, ductless) instead.
That is not an HVAC plan, and the unit you mention is not an HVAC solution! It is merely an air conditioner, which is PART of the HVAC plan, but only a small part of it. Think of this: To isolate a studio, you need two complete leaves, each of which is totally sealed air-tight, absolutely hermetic. So how will you breathe inside your studio, if there is no air going in or out, because you decided to seal off the ducts that were keeping you alive?
Here's a few questions that you will NEED to answer when you get around to designing your HVAC system: What is the flow volume, in CFM, that you will need for each room? How much of that is re circulation, and how much is make-up? What is the flow velocity at the registers? What NC rating are you aiming for? What is the sensible heat load in each room? What is the latent heat load in each room? What cooling/heating capacity do you need in each room, in BTU/HR? What is the average outdoor humidity, and what is the target indoor humidity for each room? What is the cross sectional area of the ducts that you will need to supply the correct volume of air at the correct speed, and what is the static pressure that the duct system will impose on the fan? What is the maximum static pressure that your chosen fan can handle?
If you cannot already answer all of those questions, with exact numbers, then you have a major problem, and should NOT be pulling down drywall or installing doors.
Do we also have to decouple the sprinkling system somehow from the joists?
Not just that, but for high isolation you have to decouple the sprinkler system from itself.
Wrap the pipes of the sprinkler?
Well, that would help to reduce the noise of water running in those pipes, but if you ever do have a situation where there really is water running in those pipes, then the least of your worries is noise!
We intend to add inner walls: metal frame + one side of 2x5/8" + GreenGlue, with isolation around frame as well.
What is the MSM resonant frequency of that setup? What level of transmission loss will it produce, and at what frequencies? Does that match the spectrum of the sounds that you will be producing, taking into account the equal loudness curves?
Thank you to anyone in advance for advice/guidance regarding the ceiling, which is most challenging.
It might seem that way, but in reality it is only a small part of a much greater challenge, which is to isolate the studio as a whole, not as a bunch of individual parts. Trying to isolate by looking at one door, then a part of the ceiling, then a pipe, then a wall, then an air conditioner, is pretty pointless. Isolation is a system, not a bunch of individual parts that can be isolated individually. It needs to be consider as a whole, not as separate bits and pieces. Isolation is only ever as good as the weakest point, so it is imperative to isolate the whole, together, as a complete system, and not try to do it bit by bit. Yo can't build a car by getting a wheel from a bicycle, an engine from a lawnmower, the cockpit from a 747, and the body from a nuclear submarine. Each of those parts works perfectly well when used individually, but there's no chance in hell that you could ever get them to work together as a system.
Once again, I apologize if the above comes across as being a slap in the face, insulting, or harsh. That is not the intention at all! I'm not trying to bring you down, but rather to get your attention and help you realize that you are not approaching this from the right angle at all. You originally came here looking for a studio designer, which would indeed have been the smart thing to do. But clearly you didn't actually follow through on that, and decided to do brain surgery on yourself to save a few bucks. And now you have gotten yourself painted into a corner. The only way to get back on track, it to retrace your steps, right back to the beginning, and start again: either hire a studio designer, or learn how to design the studio yourself, but whichever of those two paths you follow, it is absolutely imperative that you MUST have a complete, detailed plan. But trying to continue on the current path is doomed to failure in any one of a dozen ways. You might well end up with a room, sure, but it will not be optimal in any acoustical sense of the word, and you will have wasted a lot of time an money to get to a place that is only mediocre, at best.
- Stuart -