Sound profing an internal wall

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David321

486 posts

Ultimate Geek

#305908 13-Jun-2023 07:40

Hi all,

I am currently in the process of soundproofing (to a certain extent) an internal wall in my house.

I don't want to make the wall any thicker as that would mean cutting the carpet back and relaying the tack strip etc which I am not to keen on due to hassle and time constraints.

I have removed the gib on one side of the wall exposing the framing which is 100mm thick (old rimu), now I am looking for a good (but reasonably priced) acoustic insulation to go in the wall which brings me to my question.

I see mammoth make an acoustic insulation and their most effective one (for 90mm thick) is their r.25. The thing is, I have just insulated another wall for heat retention with earthwool glasswool in insulation which has an r value of 2.6 and is significantly cheaper the the mammoth acoustic insulation leading me to think, does the r value relate directly to the acoustic performance?

If so I feel I would be better off using the earthwool glasswool insulation as it has a higher r value, I could even get their r2.8 cheaper than the mammoth r2.5. Or perhaps their is more to acoustic insulation than just the r value which makes the mammoth superior?

Also, if anyone has an tips on further steps to sound proofing a wall id love to hear them, I am currently looking into acoustic flush boxes for the plugs and light switch on that wall also.

_David_

Torquenstein

102 posts

Master Geek

#3089260 13-Jun-2023 08:38

Below is a good resource on different options for Noise Control including cost/noise benefit.

I ended up double stacking standard 13mm in my home office but could not justify noiseline/Gib Rails. Used pink batts noise insulation and sealed with silicon all joints/ corners. Happy enough with results.

https://docs.google.com/spreadsheets/d/1JjHWJvl7y31sN2yU1QbUb13w7Pqfx7n-bMwGkj6wLIo/edit#gid=0

From what I read mass and isolation are more important for noise transfer than the insulation choice so stacking gib / double walling or in America they talk about using MVL sheet between drywall layers but couldn't really source in NZ.

Canuckabroad

179 posts

Master Geek

#3089261 13-Jun-2023 08:41

The R-value doesn't directly relate to noise-cancelling, but thickness and density do. A mineral wool like Rockwool Safe & Sound is the gold standard but is more expensive, while your standard fibreglass isn't quite as effective at dampening noise it's probably better value for money. Pick the thickest batt that will fit in the cavity and make sure there aren't any gaps just the same way you would if you were insulating an external wall. Sound will find a way through the holes or gaps in a wall just like heat does - holes cut for electrical or other wiring will allow a surprising amount of sound through unless they are contained (and again, anything that makes the wall more airtight will also decrease noise transfer).

Handsomedan

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#3089262 13-Jun-2023 08:48

Found this on the net which covers the difference between thermal and acoustic insulation, but as has been said already - it's density, rather than thermal properties or r rating that matters with soundproofing.

https://pricewiseinsulation.com.au/blog/difference-between-thermal-and-acoustic-insulation/

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mdooher

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#3089281 13-Jun-2023 09:37

One trick is to use a different density and or thickness gib on one side. eg use noiseline/braceline and even better use 13mm if that small extra thickness won't be a problem for you.

sealing up around the flush boxes and edges will make a huge difference

Without making the wall thicker you will always get transfer through the studs and dwangs, so doing much more than putting in sound batts or similar (in addition to the above) will be a waste of time

Matthew

Bung

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#3089286 13-Jun-2023 09:49

When sarked walls were gibbed it was often above the skirting. You could still add more gib without reducing floor dimensions.

tweake

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#3089484 13-Jun-2023 15:07

i suggest having a look at the actual testing of products. one lot of testing found plain old pink batts better than the noise proofing version. i suspect a lot of the noise proof high density stuff a bit of a con.

the other thing is its almost pointless to do much if you have air gaps. smaller they are the worse they tend to be for noise. try not the have power points on those walls. have a look at using sound proofing sealant between the gib and studs. a critical area can be how the corners of the wall are done.

Hammerer

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#3089579 13-Jun-2023 18:28

We have been here before so here is a similar topic from 2016 which has more useful info.

Pink Batts silencer vs normal insulation