Experiment time ( or fun with rubber )

eric · Post by **eric** » Sun Oct 05, 2003 8:51 am

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

giles117 · Post by **giles117** » Sun Oct 05, 2003 10:01 pm

I used roofing rubber. GAF Triply. Worked to knock out the low end considerably.

Bryan Giles

30'x 40" = $37.00

Post by **John Sayers** » Sun Oct 05, 2003 10:42 pm

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

well you sound insane

I must admit - some people spend too much time chasing STC instead of acoustic reponse - for me the latter is the important one.

cheers
john

eric · Post by **eric** » Mon Oct 06, 2003 1:21 am

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

giles117 · Post by **giles117** » Mon Oct 06, 2003 5:59 am

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

eric · Post by **eric** » Mon Oct 06, 2003 6:33 am

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

giles117 · Post by **giles117** » Mon Oct 06, 2003 6:54 am

No these are STC, your are asking about MTC (Music Transmissions Class)

I Think Eric Desart is the man for that info.

Bryan Giles

knightfly · Post by **knightfly** » Mon Oct 06, 2003 9:33 am

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...

Steve

Post by **John Sayers** » Mon Oct 06, 2003 10:10 am

I wasn't refering to you steve

:)

cheers
john

eric · Post by **eric** » Mon Oct 06, 2003 12:40 pm

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

blas · Post by **blas** » Mon Oct 06, 2003 9:58 pm

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!

knightfly · Post by **knightfly** » Tue Oct 07, 2003 1:19 am

"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...

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

blas · Post by **blas** » Tue Oct 07, 2003 8:35 am

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.

knightfly · Post by **knightfly** » Tue Oct 07, 2003 10:46 am

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"

)... Steve

Eric_Desart · Post by **Eric_Desart** » Tue Oct 07, 2003 11:28 am

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