Experiment time ( or fun with rubber )

I am constructing an isolation wall for a divider between a live studio room and a control room. Looking at some of the isolation sheeting (auralex etc ) I decided to try 1/2" rubber stall matting. Each sheet wieghs about 65lbs ( 30 kilos) and is a convenient 4'x7'. Has anyone tried this type of thing? I am going to sandwich it between two layers of sheetrock. Anyone who thinks I am insane please speak up now before it's too late.javascript:emoticon(':shock:') Thanks Eric

I used roofing rubber. GAF Triply. Worked to knock out the low end considerably. Bryan Giles 30'x 40" = $37.00

Anyone who thinks I am insane please speak up now before it's too late

well you sound insane :lol: I must admit - some people spend too much time chasing STC instead of acoustic reponse - for me the latter is the important one. :lol: :lol: cheers john

Well,....... I am going for both. I am using one of your room designs as my reference for construction ( with a few small changes in dimension). Thanks by the way for all the really cool reference materials. I have built a few smaller home studios in the past but this one is much larger ( 22' X 36' space with a 36' X 50" attached garage space that has a really nice sound inside). I'm really trying to do it right. That being said I thought isolation in a control room was important.Perhaps I am missing the mark? I have used all the standard double wall techniques everywhere between rooms. I was a builder for several years so construction is no problem for me and I really enjoy creating the spaces. I have been in several small studios where the drums rattle the coffee cups off the table. The goal of the whole thing is to kill the bottom end coming through the walls. Can I conclude that you think this is a bad idea? BTW I have always enjoyed my insanity errrr eccentricity. Eric

An STC of 50+ will eliminate those issues you speak of. What these guys are giving you you can result in an STC of up to 62+ A floated floor will also help with isolation of drum vibrations (kick, etc.) So don't fret, I have double walls in the CR of 1/2" and in the Live room (purely by mistake) of 2 sheets 3/8 and 1 sheet 5/8 between the CR and Live room. You can beat on the other wall, and I DO not hear it in my control room. We cut drums the other day and I never knew the drummer was there. I have floated floors in both my CR and Live room. Bryan Giles

Well, Maybe I should forget the big thick rubber wall thing then. The floor is made of concrete so I don't think that will be a problem. Does the 50 plus stc go from 20 to 20000 ? I was under the impresion it was an averaged number with mids and highs bringing up the weak bottom end isolation. So in other words lots of high frequency block and not much low end block. Eric

No these are STC, your are asking about MTC (Music Transmissions Class) I Think Eric Desart is the man for that info. Bryan Giles

STC stops at a low of 125 hZl. Nothing below that is even considered. MTC, which is kinda like DVD in that nobody seems to agree what it stands for (Either Machinery Transmission Class or Music Transmission Class) fills in the bottom octaves, down to ( I think) 30 hZ. I've yet to see a curve on MTC. STC is centered at 500 hZ, and was intended for speech isolation quantification. Two entirely different wall designs might test exactly the same for STC, but one might give 15-20 dB better TL at 30 hZ. If Eric doesn't chime in eventually, I may find time to chase down more about MTC - Main thing to remember is MASS, when you're looking for LF isolation. 3 feet of concrete is good... :? Steve BTW, John - your comments about only stoned hippies with headphones hearing the birds on a recording notwithstanding, I would prefer not to make recordings of my idiot neighbors yelling at their kids, or their barking dogs that are smarter than their masters, or race cars being given an "Italian Tune-up, etc - so I'll probably continue to worry about isolation techniques, but it doesn't mean I'm any less concerned with acoustics - I simply want it ALL... :twisted: Steve

:oops: :oops: I wasn't refering to you steve :):) cheers john

So , Knowing construction costs as I do I may be better off just building two walls to use as concrete forms. I could save a few bucks and have a place to practice handball. I have never even heard of this whole mtc thing. The more I find out about this acoustic stuff the less I seem to know for sure. I think I will try the rubber wall thing and hey if nothing else you all get a free lesson at my expense. I am waiting for the insulation crew to get back to me as to whether I can afford to have them do it. If not I will be a little richer and a whole lot itchier. I will let you all know how this goes. Eric

Eric, You're close with the rubber idea. What they have, and I used is that 1/8 vinyl mix on a roll. I placed the layer between several layers of drywall, just remember you need to glue that on PLUS the last drywall layer, as you don't want to have holes (screws/nails) thru the vinyl. Again, this is the product they use in submarines to quite the engine area. Great stuff. Good luck!

"I wasn't refering to you steve " - Sorry if I seem a little touchy on that one John, it's just that I've been refraining from setting both my neighbors' houses on fire with all residents inside for about 20 years now, sure wish it was socially acceptable to saute shitheads... :x :x Eric, I'm not sure but I think you might be better off forgetting the rubber thing - for one thing, you'd need to glue everything together and if I'm not mistaken that would make your entire wall leaf revert to having only ONE coincidence dip, which would be at a fairly low frequency, which would go through the wall easier than non-resonant ones. I've talked to people who've used 3 different thicknesses of sheet rock on a leaf of a wall, with two thicker ones on the other side, with great success. (Drums not audible, period) With glued wall layers, you lose isolation - with screwed ones, depending on your framing, you can also lose. It's kind of a tough call, for one thing I'm not interested in working in a studio with walls/ceilings that are ONLY glued, don't need things falling on me and don't want any one frequency range to bug me. I don't know if you've read these two or not - http://johnlsayers.com/phpBB2/viewtopic.php?t=598 http://www.domesticsoundproofing.co.uk/tloss.htm Those two cover most of what I'm trying to say with no sleep in 32 hours... Steve

Knightfly...Trust me brother, one layer of vinyl and the next drywall won't fall off a side wall if glued properly! And the value it represents over using something that "goes thru " a wall to reduce transfer, is worth the effort.

I can see where gluing DIFFERENT types of materials probably wouldn't be as bad as SAME ones, due to the velocity shift - and I'd not worry about WALLS falling on me with only glue - I've just always shied away from the mass loaded vinyl because it's so freakin' expensive and badmouthed by degreed acousticians as well. You sound like you've had good luck though - do you have any (semi) real test results as to actual TL with your methods, or just "enough for me", or what? I'm always open to (quantifiable) facts, and always willing to argue (oops, I meant "discuss" :wink: )... Steve

Hello Steve, I want to correct something here in relation to STC and MTC. STC originates from the European Rw, which evolved from very old German ratings. It is based on a stylized curve of a massive brick wall commonly accepted as good for separation of houses/dwellings. The idea was that an Rw or STC of 52 dB (based on a massive wall behavior) was a good house separation. The ASSUMED (but not correct) connection of STC or Rw with speech only came later, because more and more double leave systems were used, and one noticed that for a lot of noises STC and Rw weren't good parameters with the newer and interior double leaf systems. Because the weighting curve of both approximates a bit speech, one wrongly assumed a connection of the original design of those standards with speech. In fact even for standardized speech, STC and Rw aren't stringent enough. If you analyse the weighting of STC and Rw, you'll notice that it strongly resembles a dB(A) weighting. A dB(A) weighting statististically is ca 1 to 2 dB more stringent than STC and Rw (but individual deviations caused by the mathematical inacurate approach of STC/Rw can go much higher). You'll also notice, and that's where it came from, that the rize in TL of STC and Rw resembles the mass law, rizing at 6 dB/octave, which is than flattened in the mid and high frequency range. So, STC is not based on speech, but on the TL behavior of heavy brick separation walls taking the overall TL versus thenadays average household noises. MTC covers EXACTLY THE SAME FREQUENCY RANGE AS STC, and does NOT include any lower frequency. The reason MTC was developed by Stan Roller of USG, was that indeed with drywall STC and Rw completely failed for low frequent content as music. There is no doubt what MTC stands for: Machinery of Music, since Stan Roller designed it with the intent for both. MTC only adds some additional restrictions in the 125 and 160 Hz band, but it starts exactly from an STC calculation, which is than further corrected. By doing so Stan Roller could limit the effect of the mass-spring resonance, which is very defining on the insulation curve of double leaf systems. This MTC became NEVER an official standard. In fact in order to get it accepted it's based on STC calculations widely accepted, and additionally corrected. But since STC and Rw are both mathematical questionable approaches, which only exist as is since they were designed in a period that logarithmic calculations were only accessible for few, this MTC method (bit primitive) never got or will get the chance to become an official standard. That's also why it is so extremely difficult to find the calculation method for MTC, It's almost NOWHERE published. I added a file I made 1 to 2 year back (please respect copyright) exactly explaining how both are calculated. Basically the OITC, which IS an official standard, and is measured down to 80 Hz, is more accurate and better than the MTC also for music. This was also (much later) designed by an, (at the time) USG staff member: Keith Walker. This OITC is now officially in use already for windows, outside walls etc. in function of traffic. It better than MTC gives a weighting corresponding to average music from good HIFI installations, is more stringent than MTC, but basically not yet stringent enough for studio and pop concert hall use. Hope this gives a picture. The file is added, so you can check it out for yourself. Do not put this file on another site please, it's meant for strict personal use. If you want to make it a sticky note here it's OK for me. Best regards Eric

Hey Desart glad you chimed in, was looking forward to your insight. OITC is it. Good to know these things, hope things are well in Belgium. Bryan Giles

Eric, thanks for posting that - I thought I had heard you say before that MTC went lower, must have mis-interpreted. I'll read through your file a few times soon as I get a chance, is it OK if I just post a link as part of a resources page I'm working on? Again, always good to hear from you... Steve

This is great. I thought I was asking a simple question and wholly mackeral the science is staggering. This is like so many things in life where a standard is just one guys way of getting his point across. Everyone else can be on a different page and who knew? I suspect that the concepts are similar but the measuring method is different ? The problem I have is that no one seems to have published anything based on what I want to try. ( or at least not anything easily found ) Sheetrock is obviously going to give a different result since it's sheetrock and not rubber. It seems that the tests are all done with sheetrock and other standard building materials. So what's a guy to do? Anyway I am very nervous about the weight of this stuff. My plan wasn't to glue anything but to actually use laminating screws using two layers of sheetrock one on either side of the matt. Early strength test are not reassuring. The thing I get from gluing is that it may create a focused resonance? Man I am so confused. That's the price for being inexperienced and full of crazy ideas. Eric

Knightfly, I'll post later any data I can draw from using the vinyl as one of the layers, but currently (about 16 or so months into the reconstruction) I'm still too busy finishing EVERYTHING to get the studio back up and running again! The only thing that's saving my ass from so much lost revenue is/are the mobile jobs I do. Yes, you are so right about the cost of the product. But if you're a good shopper........money can be saved buying from the right place. As the old song from the 60's goes "silence is golden", today we can also add the line "and expensive too"!

"Man I am so confused. That's the price for being inexperienced and full of crazy ideas. " - Join the club - just over 20 years ago I built this room in my barn, thought I knew what I was doing - I was so bummed out when I discovered that my wife could hear what song I was playing on the piano from 100 feet away inside the house... That's what started my course of random study of all things acoustic and quiet, still at it... If you're just talking about doing walls, I'd consider glue laminating the rubber between layers on the side toward the tracking room, making that leaf effectively one layer with a "gooey center" (love those gooey centers...) if you use 5/8" sheet rock on both sides of the rubber, the 2 layers of sheet rock and the rubber combined should lower the coincidence dip of that leaf to around 27 hZ, assuming a 5.5" air gap - if you mount that side solid to the frame and mount 2-3 different thickness of sheet rock on RC to the other side of the frame, you should get a pretty impregnable wall between your CR and Studio. I'm not sure how you would go about doing the laminating, unless you made several "super panels" horizontally and put them up after laminating. The downside of that is the need to thorougly caulk between 4 x 8 panels to avoid hairline cracks that will ruin the TL of the wall. If you laminate in place and stagger joints it would be less likely to cause gaps, but I've never tried to do that with something like rubber. Guess you get to be a pioneer on that one... Blas, don't worry about that right now. Your main goal of "keeping beer in the frig" needs to take priority. If you get to it in the next year or so, we'd appreciate any feedback though... Steve

You bring up a good point in that I was considering putting the rubber panels on the inside wall of the c.r. It would actually be easier to do it as you suggest. Since they are 4'x7' I would have to do the two part thing. Just out of curiosity how on earth do you figure out that there would be a coincidental dip at 27hz? And of course thanks again for all the help folks this is great and much appreciated. Eric

Everest gives the formula in Master Handbook of Acoustics - it's Fo= 170/sqrt(M*D), where M=mass in lbs/square foot, D= depth of air space in inches From here - http://members.tripod.com/Bills_Drywall/Questions.html I got the weight of standard drywall panels - divided by 32 for 4x8 panels gives you M in pounds per square foot Air space depth is self-explanatory - 5/8 rock is 2.3125 psf, so 2.3125*5.5" = 12.71875; sqrt= 3.566335654, /170 and invert = 47.66 hZ. You added a second layer of 5/8 rock, plus 65 pounds of rubber divided by 28 square feet - so now, replace the 2.3125 psf figure with 6.946 psf - that times 5.5" (for 2x6 walls, not sure what you have) = 38.203, sqrt= 6.18, divide by 170 and invert = 27.5 hZ. That's only if you glue each layer. Otherwise, the panels need to be calculated individually. I'm not sure which would be better, gluing or not - but I wouldn't glue the panels on BOTH sides of a wall - dissimilarity is what keeps the wall from passing one frequency better than others. that's why I recommend 3 different thicknesses on a wall over 2 thicker ones... Steve

Ummm, One thing i might want to add here.......... when i visit the site of the companies that manufacture the membrane products for this use - what i have seen for new installations is to install the membrane 1st - and the 2 layers of drywall afterwards........ the sandwich between 2 layers is only reccomended for situations with existing drywall.......... Rod

Rod, I'd noticed that too - I'm assuming it would improve damping similar to having the insulation touching the inner wall layer ? I just have a hard time wanting to pay that much for something that seems like it should be much cheaper, so I tend to ignore the mass loaded vinyl more than I should. I noticed the same thing when I had to buy some heavy vinyl shower pan liner a few months ago - anybody trading in vinyl futures these days? Must be a "tunna-munney" in it considering the price... Steve

Hello All, Just to say this ones more: A mass loaded vinyl is a material with high internal demping causing a higher insulation than other materials with the same mass. However this difference is minor when compared to drywall. Combining mass loaded vinyl with any combination of drywall layers will hardly make any difference with a drywall layer combination of the same total mass. It increases the damping of the layer combination a bit, but for the same total mass you can be happy if you find individual frequency bands in low and mid improving with 1 dB (2 dB if EXTREMELY lucky). On the overall insulation it is negligible. The effect is mainly to be found at the coincidence but can easily be substituted by different drywall thicknesses = adding thin board with deviating coincidence) You can easily (in as far this is important) substitute this mass loaded vynil by an additional thin layer of drywall which will damp the coincidence (which has minor influence on music noise) as well. In the pro world a drywall with mass loaded vinyl combined in general is seen as designed by non-acousticians and not taken seriously. The price and energy versus return on investment is as bad as can be. It's simple: You find a lot of TL measurements of mass loaded vinyl on the net. But they are measured as a free-hanging autonomic object. Such sites WRONGLY (direct or indirect) suggest that those values should have anything to do with using this material in combination with a drywall. WHAT YOU NEVER FIND: An objective comparison of a good drywall design of the same mass, measured in comparable controlled circumstances wit a wall where the mass-loaded vinyl is used. What should be easier to prove their (misleading suggested) point than publishing such (scientific objective) comparison. Note: Traditional quality roofing at room temperature has comparable to better properties than PVC. A lot of the cheaper materials are based on mass loaded bitumen (roofing). The advantage of vinyl versus roofing is mainly that it works better at very low outside temperatures. PVC can't burn. As such is fire resistant. But when burned by external source the chloor in it is very poisened. Just some thoughts. My personal vision: Using mass loaded vinyl in a drywall combination should be useful if: 1) you want to spare few mm. 2) You have too much money and energy This does not mean that there aren't usefull applications but certainly not where most studio sites suggest this material should be used. Best regards Eric PS: Steve, don't confuse mass-spring resonance with coincidence. I saw your calculation which is mass-spring, not coincidence. The coincidence frequency is what in US books is often refered to as the critical frequency (wavelength incidence noise equals bending waves in panel). In general gluing layers together is wrong. It lowers this coincidence to a more critical frequency range.