floating room on a non-floating floor

fantastic site. thanks so much! I am just about to begin (friday oct 15) to build a room within a room soundproofing into our new (to us) house. I wish I had found your site earlier. I am basically trying to soundproof the studio part of the downstairs (29'x10') enough to be able to rent out the bachelor apartment that is downstairs as well. I know that is a very tall order. As well, I have quite a lot of gear including 2' analog and board, 15" Tannoys, Hammond and Leslie, Protools, ADATS, and quite a bit of outboard and guitar amps etc. etc. etc. I built and ran a studio downtown for 14 years and then got out of it for the last few years. I am very rusty on all this acoustics stuff but I do grasp some of the basic concepts. One thing that I found when we built the first studio back in "87 was that is was way better to do it right the first time. I have been thinking of just building a floating square room inside the existing one (29'x10') and then splitting th room into 2 rooms (probably 18'x10' and 11'x10') and putting up some diffusers to treat it. (Some of the wall treatments on this site look like they would be perfect for this application.) The reason for this is that I wanted to maximize the use of space in case we end up moving out and we want to turn it into a suite as well. There is an existing wood floor on concrete that I was hoping to be able to save as it looks very nice and works well. One problem there is that will be a direct connection between the two walls. I don't know how much transference that will cause in real world situation. I know it is not optimal. So I guess my questions would be, Do you think that the floor will transfer enough energy to the outer wall to be enough of a problem that I should float the floor? and, Do you think that building the room basically square and then treating it is more problematic than building a diagonal wall design? (which would not convert to a suite very well at all) Thanks in advance for your replies

Although splayed walls are better for mixing, and non-parallel rooms done correctly are better for recording, one thing rectangular rooms have going for them is predictability. However, you should NOT consider building any room with two dimensions the same, period. AS to floating or not - flanking noise will make it impossible to achieve better than about STC50 unless all interior surfaces are decoupled from the main structure. This means floating floor, walls not touching outer walls, and ceiling suspended resiliently from outer ceiling or resting on the floated walls. Anything less will disappoint you (and your prospective tenant, unless he/she LOVES your music over and over and over...) How much headroom is available to you? If you can spare about a foot, this should be easy. Any less, and we'll need to talk about your existing construction, budget, etc... Steve

the ceiling is 8 feet. what exactly do you mean by "no two dimensions the same"? oh I get it. you mean depth and width right? so rectangular as opposed to square? I was thinking of something along the lines of "Garage Studio #2" which is in the Plans section here; http://www.saecollege.de/reference_mate ... 0Plans.htm I thought that I'd build it rectangular and then treat it with diffusers and absorbers to make it non parallel. That way it could be turned into a nice soundproofed apartment if we decide to move, rent it out etc. It's hard to know how far to go with a studio in your house as it can get out of hand pretty quick. If we build it rectangular and add the diffusers etc then we can take them with us too if and when we leave. Funnily enough when we built our studio (Fluid Sound) back in the 80's we spent about a year and quite a bit of money and it was a real nice room. But you know what? I've been recording in houses a lot recently, living rooms, dining rooms etc. and I like them almost as much. Of course it helps a lot when it's full of furniture and stuff. I gotta say this is a fantasic site. It makes my head hurt tho.

What you're considering could work pretty well; but actually, I meant that no two of the THREE dimensions of a room should be the same; acoustics is 3-dimensional, so ceiling height is as much a factor as width and length. There are several so-called "ideal" room ratios that supposedly are better for sound than others, but in reality you sometimes have to live with what you have. In your case, knowing that dimensions should differ can help you choose how much of your space to make into each room. One of the "ideal" ratios, put forth by Sepmeyer, is 1:1.6:2.33 - this means that if the height were 10 feet, width should be 16 feet and length should be 23.3 feet for best modal distribution (most even frequency response) - If you were to use that ratio for an 8 foot ceiling, you'd have 80% of those values, or 8 foot, 12.8', and 18.6' - there are other ratios of length/width/height that also work well - probably the easiest way is to stay away from even numbers and ask us to calculate these for you, if you don't want to get into it that deep. It's almost 4 am here, so gotta get some sleep; if you've not already checked out some of the other stuff at the SAE site, have fun; there's a lot there, several days worth of reading if you want... Steve

I've been reading more on your site here about "3 leaf" vs 2 leaf. Very interesting, but I don't think I quite understand. In my situation for example, there is an existing room with gyp on both sides of stud wall. I was going to put up another layer of gyp on the existing wall attaching it through narrow strips of donaconda to suspend it somewhat from existing wall. Then I was going to build a floating single sided room inside of that with about a 1" gap and then I was going to put 2 layers of 5/8" gyp on the inside of the floating wall, also seperated by narrow strips of donaconda. Am I creating a 3 leaf system here? I always thought that suspending the gyp with the donaconda was beneficial. Is this correct?

First, even Google doesn't know what donaconda is - do you have a link or picture or anything? Second, what you're describing sounds more like at least a 4 leaf wall in total; and yes, that's NOT the best (or even a GOOD) way to use materials. Check the drawing out at the top of this page - http://www.johnlsayers.com/phpBB2/viewt ... 1&start=15 It shows the proper order of materials for best use. Every time you use a small air gap and more mass, you "short out" whatever sounds are at the mass-air-mass resonance of that combination of materials - by keeping all mass in only two locations, and making those two mass centers as heavy as possible with as wide an air gap as possible, you lower the mass-air-mass resonance as much as it can be. Ideally, you would want this resonance to fall at least an octave below the lowest frequency you want to isolate. Having several small air gaps in a wall construction just makes the wall weak at several different frequencies. Think of the air space in your wall as a spring; which is stiffer, one long spring or several short ones? So, with several short stiff springs separating your materials, you will have much more coupling between materials and more sound will pass through. What you need is DE-coupling; this can be accomplished by using the widest air gap between two heavy masses. Are we there yet? Steve

good stuff. thanks steve. Listen, my carpenter talked me into putting a layer of extruded polystyrene foam insulation under the 2x4 wall to isolate it from the floor. he swears that its strong enough to take the weight of the wall and ceiling without compressing, but he's been wrong before. I now have the room framed and wired and am preparing for drywalling. if this foam sarts to sag then th room could touch the other wall in places possibly. have you ever used polystyrene foam to float a wall?

Hey Steve, your conversation here raises two possibly ignorant questions in my mind. 1. what is the difference between "splayed walls" and a non-parallel room? 2. excellent point about a larger space between isolating walls being better than many small layers. what is the conventional wisdom about turning that theoritical 1 foot space into perhaps 3 or 4 feet that could be used as a closet or even bathroom? thanks, jono