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Green Glue & panels for existing walls?
Old 14th November 2009
  #1
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Green Glue & panels for existing walls?

My studio has been serving me well for the past few years, but it's main flaw is the train line which runs underground not far from the building. 95% of my sessions are completely unaffected by this, and the other 5% I am able to work round things, but I would love to improve matters.

When I moved the studio to this building, (not realising about the train line) I constructed all my rooms inside the existing concrete floored structure with wooden stud frames, on neoprene, with a double layer of 12.5 mm plasterboard, followed by resilient bar and a final layer of 12.5mm soundbloc plasterboard (with rockwool insulation behind). While this does a good job of blocking out outside noise, and sound transfer between the rooms, it has also created a nicely braced soundboard which resonates beautifully when a train passes!

I don't own the buiding, and am looking to buy somewhere in the next couple of years, so any major reconstruction work is out of the question, especially as I've worked happily and (almost) profitably here for the past six years. However, I was thinking recently that if I was to screw some sheets of MDF to the existing walls, say one sheet of MDF for every 2 boards, backed with a couple of tubes of green glue on each sheet, that this might damp the walls sufficiently to substantially reduce their resonance.

Anybody any thoughts / experience ? To do this to the entire studio would probably cost in the region of Β£1000, which if there's a BIG difference I would say is well worth it, but if it's going to be minimal then I'd rather keep the cash to save towards my own place.

Any thoughts would be appreciated!

cheers
Old 15th November 2009
  #2
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Anybody ????
Old 15th November 2009
  #3
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PaulP's Avatar
 

I'm no expert, but it seems to me that if you've got trains shaking the
entire building it would be pretty difficult to isolate yourself completely.
A quick search on "studio isolation underground trains" shows that you're
not alone and that you may need to go to great length, like suspend
your inner room on steel springs, if you want to solve the problem.
Another suggestion was to move...

Paul P
Old 15th November 2009
  #4
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jhbrandt's Avatar
Quote:
Originally Posted by PaulP View Post
I'm no expert, but it seems to me that if you've got trains shaking the
entire building it would be pretty difficult to isolate yourself completely.
A quick search on "studio isolation underground trains" shows that you're
not alone and that you may need to go to great length, like suspend
your inner room on steel springs, if you want to solve the problem.
Another suggestion was to move...

Paul P
But expert advice.

Matt, Green Glue is a Constrained Layer Damping material and is very good at damping frequencies in the voice range. However, it would probably be completely ineffective at the rumble frequencies produced by a passing train.

Well, I do feel your pain. So, unless you're making a million bucks a year in that studio, I doubt that anything you do would be cost effective. Sorry.

Sounds like you're doing ok... so, like I always say sometimes, "If it's not Baroque, Don't fix it!"
Old 15th November 2009
  #5
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Hi John,

I think if you looked at the independent test data, you would find that CLD systems can damp resonance down to the LF resonance point of the partition.

Certainly not relegated to higher frequencies.

Having said that, the extreme low rumbling is likely at frequencies well below the LF resonance point of your walls and ceilings. So PaulP's post is right on the money.
Old 15th November 2009
  #6
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Thanks Ted,

I'll have another look at that.. but aren't all the tests done to STC standard?? It is only accurate down to 125Hz. Please correct me if I am mistaken. Thanks.
Old 15th November 2009
  #7
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Hello John,

I'm sure this is all old news to you, but for the benefit of the group at large some may find this interesting.

Yes the tests are conducted to the ASTM standard E-90, which measures airborne transmission loss (TL)from 125Hz to 4000Hz. However, that's not to say that data is unavailable below 125Hz, nor that the labs are inaccurate below 125Hz.

US labs are generally felt to be accurate to 80Hz. That's part of the NVLAP Standard, I believe. What's important to consider is that while the exact TL values below 80Hz may or may not be precise, if all walls are tested at the same lab, the relative (comparative) low frequency performance of each wall can be reviewed, compared and contrasted.

So if a standard reference wall is built and data collected at 40Hz and we get 5dB of TL, we're not certain that the 5dB figure is absolutely accurate (actually, it's sure not to be), but the data is useful when we look at other walls tested similarly in the same lab at 40Hz.

The (incomplete) value is in the relative comparison of the curves, rather than the actual dB of TL.

Obviously absolute TL values become increasingly compromised as the frequencies get lower.
Old 16th November 2009
  #8
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Thanks for all the replies so far everyone - just to clarify :

I'm well aware that I have no chance whatsoever of getting rid of the train vibration without spending megabucks, and certainly not extreme low end rumble, but the noise I'm talking about reducing is the sound coming from the interior gyproc walls themselves being vibrated by the trains - if I knock on a panel, I hear the same frequencies as the train rumble, and am almost certain I have amplified the sound with my construction method.

I just want to know if the extra panels I'm proposing would reduce this significantly (even if not at the lower bass end), or whether I would have needed to use green glue between all panesl when originally constructing the walls.
Old 16th November 2009
  #9
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Quote:
Originally Posted by matt2525 View Post
the noise I'm talking about reducing is the sound coming from the interior gyproc walls themselves being vibrated by the trains - if I knock on a panel, I hear the same frequencies as the train rumble, and am almost certain I have amplified the sound with my construction method.

I just want to know if the extra panels I'm proposing would reduce this significantly (even if not at the lower bass end), or whether I would have needed to use green glue between all panesl when originally constructing the walls.
Yes, probably.

I think that you could 'fix' this a little more simply by stiffening the walls with pilasters. You can use wood 2x4s for this. Screw them vertically from floor to ceiling with the 1 1/2" side to the walls every stud or every other stud. (2 x 4s are 1 1/2" by 3 1/2".) This will reduce the wall's tendency to oscillate.. at least at that lower frequency... raising their resonant freq into the range of the current damping material (rockwool) you are already using and out of the range of the room modes, which could be adding to the problem.

This solution would cost less and take less down-time for your studio. If done well, it could add a unique attractive feature to your room, not to mention, add a bit of diffusion.

It seems like you did well on your original installation by connecting the wall only at the top and bottom plates (I am assuming), but maybe you used studs that were too small (2x4s?) for the height - for wall resonant purposes?? Wider steel studs or even 2 x 6s would have been better had you know about the rumble. Addition layers of gypsum + Green Glue would indeed increase the mass and damp vibrations much better if you had built it this way from the start. Alas, but hindsight truly is 20-20...

-- My 2 cents for that question.

some years ago I bought a little used car.. nice one and a good deal too... then i looked under the hood again after I got it home and said, "Damn! I could've had a V8!"
Old 16th November 2009
  #10
Gear Addict
 

I'm not sure I'd suggest that route of stiffening. This will drive up the resonance point... and then what? LF source problem is still there, and other LF sounds will be better heard.

Raising the LF resonance point of the wall upwards simply means that less LF will be attenuated. Not advised.

You very well may be witnessing the train resonating your walls sympathetically. If that's the case then damping the drywall would help.
Old 17th November 2009
  #11
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Thanks again, Ted and John, for your thoughts and advice. I may try fixing some 2x4 lengths to the walls in one of my smaller rooms (I have some spare) to see if this helps or worsens the matter, but I have my suspicions that it isn't going to help much in my situation.

I think probably my best bet is to try out damping the panels as I originally intended, starting by trying it out in the smaller of my two live rooms. It'll still be a gamble of around Β£200 - 300 pounds to do the room, so will have to wait til after christmas , but I'll let you know how it goes when I get round to it. In the meantime, I'll keep checking this thread to see if there's any more to think about

cheers

Matt
Old 17th November 2009
  #12
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Yes, that's true, Ted.

But he said:
Quote:
I constructed all my rooms inside the existing concrete floored structure with wooden stud frames, on neoprene, with a double layer of 12.5 mm plasterboard, followed by resilient bar and a final layer of 12.5mm soundbloc plasterboard (with rockwool insulation behind).
... and this would probably damp the higher LF resonance of the panels. - That's what I was thinking, but I can't know for sure unless I personally tap on the panels or do some tests.

Any yet, from all my research on CLD, Green Glue & additional drywall may very well be the silver bullet. ~shrug~

Matt, you may need to do some testing / analysis of your room prior to doing any treatment. We here are giving you our best guesses, based on knowledge and experience... but, of course, every project has it's own peculiarities and one size does not fit all.

Also suggested is additional trapping. But since the LF energy is most likely below 100Hz, you will need to use resonator type traps; panel, perf, slot.. etc. - damped well of course. Broadband traps do not perform optimally at these very low frequencies - especially for your particular problems.
Old 17th November 2009
  #13
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Quote:
Originally Posted by matt2525 View Post
I constructed all my rooms inside the existing concrete floored structure with wooden stud frames, on neoprene, with a double layer of 12.5 mm plasterboard, followed by resilient bar and a final layer of 12.5mm soundbloc plasterboard (with rockwool insulation behind).
I wasn't reading critically before. As I understand the above sentence, you have:

Outside structure leaf, or two;
double layer plasterboard leaf;
plasterboard on resilient channel leaf.

You have at least three leafs. The obvious thing to increase LF isolation is remove the resilient channel. Easier written than paid for unfortunately.

Andre
Old 17th November 2009
  #14
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The neoprane you use is not adequate, you need to use other kinds of rubber that are tuned to damp the vibrations of low frequency sounds such as a train. So you either remove everything or insert a new partition with proper noise control

CDM is represented on US by RPG, have a look at them

Then I would fix two layers of gypsum with GG to it, with rockwool on the middle, it might work
Old 17th November 2009
  #15
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I see you are located in Scotland and not in the US, checK Untitled Document and you might contact me for this matter.

I sell these in my country, contact me later on if you need prices
Old 17th November 2009
  #16
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Quote:
Originally Posted by avare View Post
I wasn't reading critically before. As I understand the above sentence, you have:

Outside structure leaf, or two;
double layer plasterboard leaf;
plasterboard on resilient channel leaf.

You have at least three leafs. The obvious thing to increase LF isolation is remove the resilient channel. Easier written than paid for unfortunately.

Andre
I didn't catch that either. That sounds like a Triple Leaf allright.
Old 18th November 2009
  #17
Gear Maniac
 
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Yes, I have a triple leaf structure caused by my ill-advised use of resilient channel in addition to the double plasterboard layer .

Basically when I moved into this studio and made the walls, I was using my own half-baked ideas of sound insulation (thought many decoupled walls were better), and didn't see the full picture!! If there were no trains, I'd have got away with it, noise transmission between rooms is minimal, no outside noise from major road nearby, or the mechanics in the garage next door.

The smaller of my tracking rooms was built last, with no resilient bar used, just double soundbloc plasterboard on stud with rockwool behind,with the walls built on top of a floor structure sitting on rubber strips , with the final floor sitting on rubber matting. This room is ther least affected by the train noise, but only by a small margin, and it will be the easiest to test workable solutions on (although obviously the results may be different in th other rooms, being of different construction).

Unfortunately, pulling out any walls/ layers, building new structures inside or other similar time consuming and expensive solutions are all out for me - as I said, I will be moving to my own premises eventually, and the studio has served me well as it is for the last few years, so the green glued panels are probably the only solution I can realistically afford to try.
Old 18th November 2009
  #18
Gear Addict
 

Might you be able to purposefully collapse that outer layer? It would have to really be quite collapsed. That would elimate (theoretically) the outer air cavity defining the triple leaf. Then laminate another layer of plasterboard and damp if you wish.
Old 19th November 2009
  #19
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Hi Ted, unfortunately I don't think so. I'm going to try out the extra panels / green glue idea in the small room in the new year (the one without the third layer problem). If this makes a noticable difference, I will then consider removing the outer layer in the main live room and replacing with a fresh skin (sans resilient bar!!) & green glue.
Old 19th November 2009
  #20
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Good luck. I'd be very interested in your results.
Old 19th November 2009
  #21
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I'll be sure to post as soon as I've tried out the changes in the new year, in the meantime, thanks again
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