Building Rehearsal studios in the lower level of my studio..

[GradwellHouse]

Hello All, this is my 1st post here. Lots of browsing and use of the info here but my first real need for help.

Here is my story:
I own (with a partner) a 2000sqft one level recording studio. 16 years deep and we finally bought a building, it's a 6000sqft Masonic Temple in Haddon Heights NJ (511 station ave, 08035 if you wanna google maps it). The building is 2 levels with about 2800sqft per floor and a ground level area with bathrooms and foyer. We are building the studio upstairs and are building rehearsal/production rooms downstairs. We have an Architect and Mechanical/Electrical Engineers but have run into some hard to answer questions as far as the level of isolation we can get between floors with our current design.

Here is some info on the building and our plan.

The Lower Level:
The building is 38ft wide by 70ft long and 11.5 ft high, the floor is a poured concrete slab, walls are cinder block. The upper level is supported by 3 metal posts running down the middle that supports an "I" beam that the upper floor's truss system rests on. We plan on building 9 rooms down here and feel very confident in how we can isolate the rooms from each other effectively but we need zero of this floors sound to go upstairs. Right now we have a 3 part plan (technical drawings attached). Both floors are self contained, there is no shared HVAC or Electrical to worry about between floors. This level is about 4.5 feet underground.

1st step is the "Truss diaphram" which if you are looking from the floor upwards will be: 5/8 sheet, 5/8 sheet, resilient channel, truss with insulation in the truss work. I believe there is 1ft 11 from the bottom of the truss to the upper levels decking. Sheet rock would go all the way to the cinder block walls and get sealed there. The truss is of 2x4 wooden construction spaced 16 inches OC.

2nd Step: "Isolation diaphram" 2 inch gap and then a complete structure that will be 2x10 wood joist (ceiling), 2x4 studs (walls) with 2 layers of 5/8 sheet and insulation for all the surfaces (ceiling, and exterior walls) the vertical walls will floated off the cinder block walls about 4 inches and the whole structure will be supported in the center by a new set of beams and posts that run the length of the building. The posts holding up the "I" beam for the truss system would be framed, insulated and double sheeted.

3rd Step: "Room Diaphram" Rooms will be built on the slab, inside of the Isolation Diaphram and be constructed the same way, 2x10 wood joist with 2 layers of 5/8 sheet and insulation. The adjoining walls between rooms will be staggered stud, double 5/8 and a resilient channel on one side.


Here come the questions:

1. How effective do you think this setup will be for stopping a loud rock band rehearsing (115db-ish) from getting into our studio space upstairs?

2. Is there a more cost effective or easier way to get the same or better results?


Any general opinions on this design are welcome.

[stevev]

those drawings look to me like you'll end up wih a 4 leaf system between your lower and upper floors. That's not good for bottem end isolation, which a loud rock band makes a lot of.

You only want a two leaf system, and your existing upper floor is one of those leafs. That leaves one leaf for the ceilings of your downstairs rooms. For 115db of isolation you'll need something akin to a floated concrete ceiling, but that's not for the faint hearted or anyone without a load of cash.

but we need zero of this floors sound to go upstairs.

How effective do you think this setup will be for stopping a loud rock band rehearsing (115db-ish) from getting into our studio space upstairs?

I think you'll be beaten by the laws of physics for zero transmission between these floors with 115db band underneath you. Unless you have a massive budget

I believe I've read about a studio on here (or possibly only referenced here) that got 110db of isolation...with a budget that went in to the hundreds of thousands.....


I think you're going to need to re-think your isolation goals and also re-work the 4 leaf design down to two leafs.

all the best,

Steve

[GradwellHouse]

do you think a poured concrete slab as a floor for the upper level would be more effective? We had talked about that previously but moved on for cost reasons. We dont have $500k to do this but we also dont only have $50k either so I would love to hear about some options. It needs to be done right so we are willing to spend the money. Less would be better

[GradwellHouse]

Also....if we ditched the "truss diaphram" sheet rock and made the "isolation Diaphram" and the upstairs floor our 2 leafs how much space below the isolation diaphram would we need to leave to have the rehearsal rooms not be considered a leaf in the system above?

I cant see how we can not have them be rooms inside of this room that those upper leafs are creating and get isolation that will be good enough.

Steve

[stevev]

do you think a poured concrete slab as a floor for the upper level would be more effective? We had talked about that previously but moved on for cost reasons. We dont have $500k to do this but we also dont only have $50k either so I would love to hear about some options. It needs to be done right so we are willing to spend the money. Less would be better

I think one of your leafs (if not both for 100db isolation) is going to need to be quite massive, which concrete is. And yep, it certainly needs to be done right.

Also....if we ditched the "truss diaphram" sheet rock and made the "isolation Diaphram" and the upstairs floor our 2 leafs how much space below the isolation diaphram would we need to leave to have the rehearsal rooms not be considered a leaf in the system above?

lose the truss diaphram, lose the isolation diaphram and you have your two leafs. As soon as you have a big flat surface you have a leaf. Your upper floor is leaf one, your 'rehearsal room' sheet rock is leaf 2. The bigger the air gap between these the better.

I've got to say, for the kind of build you're looking at I think you need to be talking to an archirect who has significant experience in studio design and construction. Looking at these drawings I would say that your architect has not considered (or does not know about) the properties that are required for high levels of isolation.

Effectively none of those drawings look like the most effective way of isolating high levels of sound and especially in the bottem end.

Andre, one of the really experienced members here has a saying.....'studio construction is 90% planning and 10% construction'. For the kind of isolation you're looking at you'll really, really need to do your research properly.

I'm hoping that Stuart might also drop past on this thread as he would be able to give you the maths that determine the kinds of surface densities you'll need to isolate to such a high level, which will in turn give you a ball-park idea on what that isolation will cost. My guess is that you're definitely in the hundreds of thousands to get that much isolation.

all the best,

Steve

[Soundman2020]

Hi there GradwellHouse, and welcome to the forum! Sorry I didn't reply sooner, but I was out of town all last week...

feel very confident in how we can isolate the rooms from each other effectively but we need zero of this floors sound to go upstairs.

That's fine, but those are subjective statements, not objective. You should put numbers to those, as in "we are aiming for 60 dB isolation between rooms on the ground floor, and 50 dB isolation, including flanking paths, between the ground floor and the second floor"... of course, replacing those numbers with whatever your numbers are. Unless you have specific numbers set as your goal, it's pretty much impossible to design for isolation. What I call "very effective" isolation between rooms might be total overkill for you, or it might be totally unacceptable. It all depends on your own personal view of what "very effective" happens to mean. Same for "zero" transmission upstairs: "zero transmission" is actually impossible, since any sufficiently sensitive instrument would still detect it, but it could nevertheless be way less than the threshold of hearing.

As a point of reference, the best isolated studio on the planet is probably Galaxy Studios, in Belgium. They have achieved extreme isolation of around 100 dB between rooms. That's about the limit of what is technically and economically feasible, and is about as close to "zero transmission" as you could ever hope for. Even Pink Floyd themselves playing on their live rig in one room would be inaudible in the next room. But if you were to fire a gun in one of their rooms, it would still be audible in the next room, faintly. So there's no such thing as "zero transmission", even in the best of studios.

1. How effective do you think this setup will be for stopping a loud rock band rehearsing (115db-ish) from getting into our studio space upstairs?

Not very effective at all for low frequencies, sine that is a four-leaf system you are proposing there! Steve already pointed that out. Each time you add a leaf to an isolation assembly, you REDUCE the low frequency isolation with respect to what it would have been using the same total mass and same total thickness using a two-leaf system.

2. Is there a more cost effective or easier way to get the same or better results?

Yes! Absolutely! Do it as a proper fully-decoupled two-leaf MSM isolation system. That is the most cost effective method for high levels of isolation. Adding more leaves reduces low frequency isolation. It does improve high-frequency isolation, but for a loud rock band, what you need is LOW frequency isolation, since HF will always be much better than LF in any case.

Yes, if you do have to build a multi-leaf system for whatever reason, then you can compensate for the lost low frequency isolation by adding more mass and increasing the overall thickness of the barrier, but of course that increases complexity, cost, and time. Doing it with a conventional 2-leaf isolation system, is far simpler, less expensive, faster, and more effective.

We have an Architect and Mechanical/Electrical Engineers

That seems to be part of the problem: I'm sure those guys are really good at what they do, but acoustic isolation isn't really the specialty of either architecture or electrical engineering. You probably should get an acoustician on board too, to work along with your architect on the design.

I believe I've read about a studio on here (or possibly only referenced here) that got 110db of isolation...with a budget that went in to the hundreds of thousands.....

Close! But I think you are thinking of Galaxy, where they get about 100.7 dB. The Van Baelen brothers don't publicly say how much it cost them, but most guesses are in the millions of dollars...

do you think a poured concrete slab as a floor for the upper level would be more effective? We had talked about that previously but moved on for cost reasons. We dont have $500k to do this but we also dont only have $50k either so I would love to hear about some options. It needs to be done right so we are willing to spend the money. Less would be bette

There are several ways you could go here, but yes, a concrete slab floor for the upper level would be one option. However, since you do seem to need high levels of isolation, you may need to consider the option of floating another floor above that one, and building your upper rooms on that floated floor. That would certainly get you what you want, but the cost might be prohibitive.

I cant see how we can not have them be rooms inside of this room that those upper leafs are creating and get isolation that will be good enough

A 2-leaf isolation is a tuned system, and it is a case of "the whole being greater than the sum of its parts". If you add up the total mass on each of the leaves then use the normal Mass Law equations for figuring out your transmission loss curve, you would be disappointed, because you'd be looking at "the sum of the parts" in that case. But since 2-leaf is a tuned system, it greatly extends the degree of isolation (transmission loss) because it is based on the laws of resonance, not the laws of mass. Resonance is a powerful beast: it can destroy bridges and buildings when things happen to add up wrong, but when they add up right, it can do an amazing job of isolating acoustically. A 2 leaf wall, ceiling or floor is a resonant system, because the leaves on each side and the air trapped between them act like twp chunks of mass with a spring between them. When something causes one of those leaves to vibrate, one of two things can happen: if the frequency of that vibration just happens to match the resonant frequency of the system, then all hell breaks loose: the vibration is transmitted easily, and is in fact amplified by the system, so it gets louder and louder on the the other side. But if the frequency of the vibration is more than about 1.414 times higher than the resonant frequency, then hell does NOT break loose! In fact, the system very much does NOT want to resonate at other frequencies, and it refuses to do so: at all frequencies above 1.414 times resonance, it isolates much, much better than Mass Law can. Mass law says that isolation increases by 6 dB per octave, but resonance law says it increases by at least 12 dB per octave, and as much as 18 dB per octave, depending on some factors. But even at "only" 12 dB per octave, it is still four times better than mass law, subjectively.

So, even though it does not seem to be possible intuitively, the laws of math and physics do not lie. This is not intuitive at all, but there's a classic diagram that illustrates the principle:

2-leaf-3-leaf-classic-walls-diagram-MSM-walls

It shows the case of starting with a typical simple house wall, on the left, then shows how the isolation changes as you do various things to that wall: adding insulation inside increases isolation by 3 points, building another identical wall next to, to make a four-leaf such as yours, increases by another 4 point. But then REMOVING the two inner leaves from that construction INCREAES isolation by a whopping 17 points, and re-using what you removed in a more intelligent manner adds about 6 points. You can see that the greatest increase, by far, comes from making a 2-leaf wall instead of a 4-leaf wall, using the exact same materials and thickness.

What you are proposing with your 4-leraf system is the "STC-40" case, third from left. What we are proposing is the "STC-63" case, on the right, which objectively isolates about one hundred times better (in terms of how much energy it blocks), but subjectively isolates about 4 times better. For less cost, and faster build.

Looking at these drawings I would say that your architect has not considered (or does not know about) the properties that are required for high levels of isolation.

I agree very much with what Steve said there. Architects are not trained in acoustics, so it isn't his fault if he doesn't know how to figure it out. But you really should have someone who knows about acoustics working with you here. The architect and the acoustic designer should work together, to make sure that your facility works both acoustically and also aesthetically, and the mechanical engineer should keep them both in line, in terms of what can actually be built physically at reasonable cost, and the structural engineering that keeps it all standing up!


That's my $ 0.02 for the day!

- Stuart -