Physics of rubber question

I've had this question for a while so I thought I'd ask. Let me first explain what it is that I'm asking. From what I've learned, rubber products seem to have 2 main uses when dealing with sound isolation: 1) as a "spring" when floating something (walls, floors etc.) 2) as a "decoupler" (neoprene pipe sleeves, neoprene used in sway braces etc.) My question is when rubber is used for "decoupling" purposes (the 2nd example above), what is it that makes the use of rubber in this context effective? Or, in other words, if the rubber is not being used for it's spring like properties, what other physical property of rubber is utilized when used for "decoupling"? I've read many times on this site and others that for rubber to be of any use, care needs to be used to ensure proper compression. Why does this principle seem to not matter when used with sway braces or other products (i.e. used as a decoupling agent?) Hope this makes a little sense. Just interested in learning a little more about this, hopefully.

cyeazel wrote:

I've had this question for a while so I thought I'd ask. Let me first explain what it is that I'm asking. From what I've learned, rubber products seem to have 2 main uses when dealing with sound isolation: 1) as a "spring" when floating something (walls, floors etc.) 2) as a "decoupler" (neoprene pipe sleeves, neoprene used in sway braces etc.)

From my perspective they are one and the same.... the only reason to bother with the expense it takes to "float" something is for the purpose defeating flanking paths - and this is isolation - so I don't understand your distinction of the 2.

My question is when rubber is used for "decoupling" purposes (the 2nd example above), what is it that makes the use of rubber in this context effective? Or, in other words, if the rubber is not being used for it's spring like properties, what other physical property of rubber is utilized when used for "decoupling"?

As I noted above - it's always used for it's spring like capabilities......... and when it is compressed correctly (actual load is determined by it's shore hardness) then it will isolate........

I've read many times on this site and others that for rubber to be of any use, care needs to be used to ensure proper compression. Why does this principle seem to not matter when used with sway braces or other products (i.e. used as a decoupling agent?)

Could you please giove a link to something that illustrates what you are saying above? I ask this because it doesn't matter what type of isolation - or the point of connection of that product - but ALL isolating products are based on spring compression - that includes isolating sway bars, etc. Rod

Rod Thank you for taking the time to respond. Sorry for the poor choice of wording. I thought that that might be confusing. So let me ask a more specific question. When using a pipe decoupling sleeve (Mason Industries has one that I'm looking into), is the sleeve acting as a spring even when used on a pipe passing vertically through a ceiling?

cyeazel wrote:

Rod Thank you for taking the time to respond. Sorry for the poor choice of wording. I thought that that might be confusing. So let me ask a more specific question. When using a pipe decoupling sleeve (Mason Industries has one that I'm looking into), is the sleeve acting as a spring even when used on a pipe passing vertically through a ceiling?

Give us a link so we can view the sleeve - typically what happens with a sleeve is that the decoupling is accomplished through the pipe never touching the sleeve itself - and then being locked in place with a stuffing of insulation (or lightly packed rock wool) - and then sealed ends - But that would be a rated assembly - so I wonder if what you are actually viewing isn't more intended to decouple the pipe (itself) each side of the ceiling.... regardless - I cannot comment on what only you can see........ please provide the link. Sincerely, Rod

Rod here is the link to the Mason product. http://209.200.80.33/html/sws_pipe_seal.htm So when vibrations cause the ceiling to move (sway) in the horizontal direction (side to side), is the sleeve then compressed thus isolating the ceiling from the pipe or am I way off? Or is this the wrong product for what I'm trying to accomplish?

cyeazel wrote:

Rod here is the link to the Mason product. http://209.200.80.33/html/sws_pipe_seal.htm So when vibrations cause the ceiling to move (sway) in the horizontal direction (side to side), is the sleeve then compressed thus isolating the ceiling from the pipe or am I way off? Or is this the wrong product for what I'm trying to accomplish?

Basically - this works by isolating noise from within the pipe from the structure - nothing else is intended. This is not an anti-sway brace. So if the pipe were (for example) a roof drain - then in heavy rains the rushing water noise (in the pipe would not be transfered into the floor/ceiling assembly - or wall assembly (depending upon pipe direction) BUT - in order for this to work all hangers and seismic braces would also have to decouple. FWIW - this works quite simply by not connecting the 2 sleeves by more than the 2 little fins you see (one top - one bottom) and not buy any sort of compression/tension system. The closed cell sponge is very VERY lightweight - and is just intended to be enough to create a permanate backer for the caulk seal required at the pentration. ROd

Rod, So to make sure I'm understanding you correctly, this particular sleeve would not be effective in isolating noise transfer from the drywall ceiling to the pipe? The pipes are sprinkler pipes so I don't need to worry much about water flow noise. I'm more concerned about sounds from within the studio flanking through the pipe system. Is there another product that would be more effective for what I'm trying to accomplish? Just so you know, the inner leaf ceiling will be hung from Kinectics ICW isolators. Just wanted to let you know in case this had any influence on product choice/performance etc, etc..

cyeazel wrote:

Rod, So to make sure I'm understanding you correctly, this particular sleeve would not be effective in isolating noise transfer from the drywall ceiling to the pipe?

Cy, 1st off - yes it would be good for that (except for another problem we have that I will address in a moment) Bang on the ceiling all day long with ths in place - and nothing of any consequence will transmitt through the pipe. But that is a seperate issue from your real question - which is :

I'm more concerned about sounds from within the studio flanking through the pipe system.

In oder to deal with that you have to seperate the pipes from one section from the pipes in section 2. I have done this (in the past) by using these products along with applying for (and receiving) a modification of the Sprinkler Code (because they do not address anything like this...... And that is with these on either side of the wall or ceiling/floor http://tinyurl.com/yp6orq Adding your sleeve between the 2 for the actual penetration wouldn't be harmfull either. BUT - note that this is not necessarily code compliant - and you would probably require a modification from NFPA 13 from the AJA Fire Marshal AND that the frequencies these are designed to handle are in the frequency ranges of pumps - not other mchanical methods of introducing noise into pipe systems. Rod

Rod

In oder to deal with that you have to seperate the pipes from one section from the pipes in section 2.

So what you are saying is that I would actually remove an existing steel connection fitting (mine mostly occur at the 90 degree turns) and replace it with the Mason safeflex product? Is this the correct interpretation of the application of this product?

BUT - note that this is not necessarily code compliant - and you would probably require a modification from NFPA 13 from the AJA Fire Marshal AND that the frequencies these are designed to handle are in the frequency ranges of pumps - not other mchanical methods of introducing noise into pipe systems.

Would the higher range frequencies in music be problematic with the safeflex connectors? You mentioned that you had used this product in the past. Was this for a studio? If you've used it in the past, then I've got nothing to worry about.

cyeazel wrote:

Rod

In oder to deal with that you have to seperate the pipes from one section from the pipes in section 2.

So what you are saying is that I would actually remove an existing steel connection fitting (mine mostly occur at the 90 degree turns) and replace it with the Mason safeflex product? Is this the correct interpretation of the application of this product?

Well they don't make 90's - so it would have to be introduced at a straight length of pipe - but yes - the idea is to introduce one of these each side of the assembly you are penetrating -

BUT - note that this is not necessarily code compliant - and you would probably require a modification from NFPA 13 from the AJA Fire Marshal AND that the frequencies these are designed to handle are in the frequency ranges of pumps - not other mchanical methods of introducing noise into pipe systems. Would the higher range frequencies in music be problematic with the safeflex connectors?

This happened to be the method of decoupling from the sprinkler systems protecting the building that was housing Power Station New England and the continuation of that system for the recording studio itself. BUT - we were very carefull to make all of the structural connections of the former to the former only - and then also supported the sprinkler for the studio directly off the studio structure only. So this was a simple matter - and only the one fitting had to be dealt with. In your case I would guess that this migfht be a bit more problematic. You pipe exists - and I can pretty much safely bet that that there isn't a decoupling hanger existing in the entire assembly. You also don't have a design that takes into account the entire project - and might find it difficult to find a single point capable of feeding the entire studio itself without creating a problem in some other area...... Sprinkler systems get pretty deep - you really should be speaking with whatever contractor you are going to be doing business with..... You completely blew past the code issue and don't think that because I figured out a way to convince a fire marshall that this would be OK _ means that it will be easy for you to do so.

You mentioned that you had used this product in the past. Was this for a studio? If you've used it in the past, then I've got nothing to worry about.

I did't say I used it in the past - I said I've used these products (meaning similar - mason industries did not have these products when I constructed Power Station - but there were similar products arouns - I beleive we were actually approved based on a installing a high pressure braided wire wrap on a high pressure reinforced rubber hose (a simple braided hydraulic hose coupling) just because the inspector recognized that we far exceeded the pressure needs of the system uitself (thousands of PSI of capacity versus 100's of PSI of needs. NFPA has since accepted the use of braided reinforced isolation feeds for individual branches - but has not (as of yet) accepted it as a method of isolating mains. And with this information in hand - you might have an uphill battle to convince even me that this should be approved as a modification. Good luck. Rod

Well they don't make 90's - so it would have to be introduced at a straight length of pipe - but yes - the idea is to introduce one of these each side of the assembly you are penetrating

So would this include any penetrations made on both inner and outer leaves of mass, or just the inner leaf?

BUT - we were very carefull to make all of the structural connections of the former to the former only - and then also supported the sprinkler for the studio directly off the studio structure only. So this was a simple matter - and only the one fitting had to be dealt with. In your case I would guess that this migfht be a bit more problematic. You pipe exists - and I can pretty much safely bet that that there isn't a decoupling hanger existing in the entire assembly.

That is correct. All the support hangers are rigidly attached to the outer leaf. So in addition to the flexible pipe connectors, I'd also have to replace the existing hangers inside the studio shell with resilient hangers? Wouldn't isolating the small sections of the system that penetrate the studio be enough? Sorry if I'm not clear on this.

You completely blew past the code issue and don't think that because I figured out a way to convince a fire marshall that this would be OK _ means that it will be easy for you to do so. Quote: You mentioned that you had used this product in the past. Was this for a studio? If you've used it in the past, then I've got nothing to worry about. I did't say I used it in the past - I said I've used these products (meaning similar - mason industries did not have these products when I constructed Power Station - but there were similar products arouns - I beleive we were actually approved based on a installing a high pressure braided wire wrap on a high pressure reinforced rubber hose (a simple braided hydraulic hose coupling) just because the inspector recognized that we far exceeded the pressure needs of the system uitself (thousands of PSI of capacity versus 100's of PSI of needs.

I understand there are many legal issues to deal with. I didn't mean to come off as blowing that off. I know you're just watching your own back on that one. It's understandable. I just want to get a good understanding of how this potential solution may or may not work. Your advice is greatly appreciated.

If your only concren is sound that physically travels through the pipe alone -and not ambient noise from that in the surrounding space...... then seperating each penetration will suffice. Flex-heaad Industries manufacturers an approved proved non-rigid connector (that acts as an isolator) for the final connection to the sprinkler heads themselves - perhaps this is what you should persue...... http://www.flexhead.com/pdf/Flexheadrprnt_1103.pdf Sincerely, Rod

Rod I just went to the flexhead home page and am excited about this option. Thanks for the link. My situation would be pretty close to this picture http://www.flexhead.com/commercial/commercial.html minus the lightweight ceiling obviously. Anyway, if I were to do this, then would I be correct in saying that I wouldn't even need to worry about the new inner ceiling touching the head itself because of the flexible hose? Or should I still leave a gap around the head and caulk with acoustic sealant? Again, thanks for your guidance. The more I gain insight from a trusted source such as yourself makes me feel more confident that I can properly guide my contractor.

Cy, I would still caulk the penetrations. Rod