2x4 w. R-13 VS serenity mat or rubber underlay for floor??

Hello again. been crunching the numbers, and am curious about all these 'underlayments' and 'serenity mats' like this one http://www.soundisolationstore.com/10mm ... yment.html and this one http://www.soundproofingcompany.com/sou ... -underlay/ the question no one seems to be able to answer is: Are these comparable in any way to an actual 2x4 frame on joist isolators with R-13 insulation?? the 2x4 seems to come out quite a bit cheaper (aside from the potential extra labor) and my instinct tells me that it would also be a more effective insulator. i have a plywood floor that sits on top of a 1x6 (2x6?) layer of boards, which in turn sits on top of 15" deep joists (the ceiling below me). i am attempting to float / isolate myself from the noise coming from below. initally i hoped to be able to do this from the underside (there's NO insulation there now, just the bare joists) but that's not an option anymore.. so i'm going to have to do it on my side (the top side) i have plenty of ceiling height here, so the 2x4 route is not a problem, in that regard. i would just love a definitive answer along the lines of: "Absolutely, no contest, the 2x4 / joist iso / fiberglass is ALWAYS the better choice..." or something... any advice would be greatly apreciated!!! thank you all! Husky

the question no one seems to be able to answer is: Are these comparable in any way to an actual 2x4 frame on joist isolators with R-13 insulation

You are looking at two entirely different solutions, to two entirely different problems. A floor underlay decouples the surface above from the actual subfloor, in order to prevent impact noise from getting into the structure, or at least reduce it considerably. 2x4s on rubber isolators are a misguided attempt to float a floor, that is doomed to failure. It's a myth, and a waste of money, because all you end up doing is building a resonant cavity below your floor that will damage both the room isolation and the room acoustics. In effect, you turn your floor into a drum. People try to do it this way when they don't understand what it takes to REALLY float a floor. I would suggest that you read this thread (link below) on how to float a floor properly: viewtopic.php?f=2&t=8173 Yes, you do see some attempts to do that "rubber puck" thing, but strangely enough, you almost NEVER see people reporting back on how it worked out for them. I wonder why... :) One of the very few cases of an honest studio builder who did that, is here: viewtopic.php?f=2&t=8134 So if you want to float your floor, then don't get sucked into the snake-oil mythology of 2x4s on rubber pads with plywood on top.

i am attempting to float / isolate myself from the noise coming from below. ... initally i hoped to be able to do this from the underside

That is, indeed, the best and cheapest way to do accomplish what you want: Resilient Channel across those joists with two layers of 5/8" drywall and 6" of mineral wool in the cavity would do a fantastic job of decoupling you from the the air-borne noise rising from down below. If that is your goal, then that is absolutely the best, quickest, easiest, cheapest and most effective way to do it.

but that's not an option anymore.. so i'm going to have to do it on my side (the top side)

That's a pity, because now your options are much more limited, and much more expensive. The "isolation mat" solution is not going to do what you want, since that is not what it is designed for. What those mats do, is to prevent impact noise from getting into the subfloor below you. "Impact noise" means things that actually knock, bang, vibrate or thump on the floor surface, in physical contact, such as people walking on it, drummers playing drums, or guitar and bass cabinets resting on the floor. All of those transmit the vibration directly into the building structure, where it travels throughout the building very well. Those isolation mats prevent that from happening, keeping impact noise out of the structure. But they do NOT float the floor, and therefore will not accomplish what you want. If the problem were your neighbor downstairs complaining about you thumping on his ceiling, then that would be the solution. But the problem is airborne noise coming form below, so that won't have much effect. It will help to a certain extent, but nowhere near what you would get from floating a floor properly (as outline in the threads above) or from simply hanging a ceiling down below on resilient channel

i would just love a definitive answer along the lines of: "Absolutely, no contest, the 2x4 / joist iso / fiberglass is ALWAYS the better choice..." or something...

I've been as definitive as I can here! The 2x4 / joist route will NOT get you where you want to go, simply because it does not work as advertised by the "myth mongers", and neither will the isolation mats do what you want, because they are design to solve a different problem. The only two things that will work are, firstly, isolating the ceiling below you (fast, cheap, easy, effective), or building a proper floated floor (slow, complicated, expensive, but also effective), done correctly, not the way the ignorant myth-mongers say. - Stuart -

Wow, thank you for that, Stuart. VERY informative (and definitive :-)) indeed! it's too bad i couldn't get into the space below to do the insulation in their ceiling. i guess i'm pretty stuck at this point. the 'underlay' issue makes total sense.. thanks for clearing that up. sounds to me like there are a lot of people / sites out there ready to sell you whatever they've got, without really standing behind it. i explained very clearly to the gentleman at one of these underlay sites what my situation was, and he was convinced that the rubber mat PLUS two layers of OSB plywood with GG btw would be 'a great solution'. amazing, right? re. the 2x4 frame issue.. that's a strange one for sure. my common sense would tell me that for airborne noise from below (ambient noise, people talking, boombox on the floor, etc) a layer of fiberglass insulation would help, no matter what. Add to that two layers of OSB with GG and there MUST be some advantage - in the BROADBAND area, no? i can totally see that the LOWER frequencies are going to be harder / impossible to get rid of, but perhaps the tradeoff btw the odd resonant low freq. vs the general broadband noise reduction is an ok one? keep in mind, I am not expecting to get rid of low low rumble.. i.e trucks driving by, etc etc - i've made enough records and worked in enough studios to know that that stuff is next to impossible to alleviate. anyway.. some questions, again. not trying to be difficult here at all! just making sure we're on the same page. a colleague of mine did the 2x4 / isolators / fiberglass in his studio (vocal booth) on top of a restaurant, and he's quite happy. am i way off in my assumptions here? again, thank you for your time. this is invaluable, for sure! Husky

sounds to me like there are a lot of people / sites out there ready to sell you whatever they've got, without really standing behind it.

Yup! In general, if the claims sound too good to be true, then they probably are. There are no "magical" products that bypass the laws of physics.

my common sense would tell me that for airborne noise from below (ambient noise, people talking, boombox on the floor, etc) a layer of fiberglass insulation would help, no matter what.

Actually, fiberglass insulation is pretty lousy at stopping sound... If you think about it, fiberglass insulation is basically just a bunch of open air, with some fibers in it, and sound goes through air pretty well... Think of it this way: a sponge in your kitchen is a really good way of mopping up water that spilled some place you didn't want it, but it if you hold that same sponge across the end of your water tap, it does nothing at all to stop the water coming out! Same with insulation and sound: it is really good at mopping up sound that "splashed" in the wrong place, but lousy at stopping sound form getting into or out of the room. Just like the sponge... That's the problem with intuition and common sense: acoustics, the way sound REALLY works, isn't all that intuitive or sensible at first glance, ... until you understand the basics of how it works in reality, then it actually is intuitive. Because we can't see sound, and watch how it interacts with objects, our intuition doesn't really have anything to go on, so we assume things that simply aren't true. If we could actually see sound waves moving around the room, we'd find it a a hell of a lot easier to understand them!

i can totally see that the LOWER frequencies are going to be harder / impossible to get rid of, but perhaps the tradeoff btw the odd resonant low freq. vs the general broadband noise reduction is an ok one?

That depends on your needs, and your music. If you are mixing dance music with a heavy bass beat, then "general broadband noise reduction" is not going to help very much in convincing your neighbors not to call the cops! But if you are only mixing piccolo music and soft romantic soprano vocals for love ballads, then "general broadband noise reduction" might be just right....

keep in mind, I am not expecting to get rid of low low rumble.. i.e trucks driving by, etc etc - i've made enough records and worked in enough studios to know that that stuff is next to impossible to alleviate.

It can be done, but the cost .... :shock: :!:

a colleague of mine did the 2x4 / isolators / fiberglass in his studio (vocal booth) on top of a restaurant, and he's quite happy.

Does your friend have the exact same building construction as you do? :) If not, then you cannot compare. Even small differences in sizes, volumes, materials, and construction techniques can make a big difference in the final outcome. Also, "happy" is not really an acoustic term that can be measured, or plugged into equations. :shot: I've been in many rooms where the sound was just plain awful, and all over the place on my acoustic analyzer, but the people in there were "happy"... until I fixed the issues, and let them hear what it SHOULD sound like. Then they attained a whole new level of "happy"! :) Their original definition of "happy" proved to be a totally inadequate measure of the quality. Let me illustrate: If you only ever ate at McDonalds your entire life, you could very well be "happy" with that... until someone takes you to a good steak house. :) - Stuart -

Thank you for all this, Stuart!! huge help!! i'll take all this into consideration, and regroup. thanks again!!! H