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Airborne sound insulation - what do the numbers mean?

Discussion in 'Room Acoustics / Isolation / Treatment' started by Ramshackle, Jun 3, 2014.

  1. Ramshackle

    Ramshackle Active Member

    I'm doing some research on converting my garage/basement (the house is on a hill so the back wall of the garage is essentially underground) into a rehearsal/listening/recording room.

    I've been looking at 3 different wall systems from British Gypsum


    They offer different levels of sound insulation, with the downside being larger footprint and/or price.

    But...I'm not sure how much is enough?? The performance of the wall systems are given as airborne sound insulation and depending on the wall construction is between 61 - 80 (Rw dB).

    Have no idea whether 61 would be adequate or not?? Can anyone explain these numbers to me and give an example(s) of how this relates to 'real' things (i.e. the level of a guitar being strummed or something...)

    I'm not saying too much about the construction and layout of the garage as I really would like to get my head around what the numbers mean and then start a new thread discussing the rest....

    Potential noise sources:

    - We are on a cul-de-sac, so there will be little traffic noise (the odd car going past at 10mph, or engine starting). I'm more concerned about weather (wind and rain noise), and noises from the adjoining garage on one side and the adjoining hallway on the other. So, people talking etc, the sound of stuff being moved around, a car pulling into the garage.

    - I don't want noise leaking out either. I guess this is potentially easier than most problems as we will not be using large drum kits, bass amps etc. Mainly acoustic instruments and vocals.
  2. Ramshackle

    Ramshackle Active Member

    Hmmm...it seems like perhaps these system walls are not the best choice for me then?

    From what you are saying, I could get far better attenuation with your brick/rockwool/plasterboard solution, and that the total thickness would be <300mm?
  3. Space

    Space Well-Known Member

    " I'd build a two sided room within a room."

    Now right here when you instruct the poster to actually build a 3 leaf assembly do you have any information to help him to understand that this type of wall assembly will result in a decrease in transmission loss at low frequencies?

    I am out of town and can not address this issue over a phone typing system....but I will when I get in.

    Ramshackle...do not listen to what this person is saying and assume he knows something.

    He knows something....he does not know enough to help in this issue and will cause you problems...do not let his long winded ness be confused with authority..it is all hack talk.
  4. Ramshackle

    Ramshackle Active Member

    Well, all interesting replies. I still haven't got the answer to my original question...what do those numbers mean? Is it good enough for what I want to do, or is there not enough information there? (Or is it plain not good enough?)

    I'm looking at these solutions because:
    a) they are tried/tested and have published performance numbers...what ever they mean. If I can figure out how that relates to what I want to do, then I'm inclined to trust them more...
    b) I know these wall assemblies are used in commercial buildings - cinemas, offices where sound insulation is important, radio stations etc... It's advertised on the british gypsum site. But I've not heard of them being used in recording studios...but I'm not building a 'full blown' recording studio. More a glorified rehearsal space with the capacity to do a bit of recording and mixing. No drums or amps (ever - we go elsewhere when we want amps. We would use some small percussion in this space).
    c) The various materials to build these walls is readily obtainable here in the UK (B&Q, TravisPerkins and other places seem to carry most of it, even the more specialist plaster board types (the 'soundbloc' board for example)) and by my calculation would be cheaper than all the wood required for a staggered stud wall...

    Reading the replies makes me think that perhaps go right ahead and start a new thread with the floor plan and what I want to do...
  5. paulears

    paulears Well-Known Member

    I checked the rules and there is nothing there to cover having different opinions, that have worked for me. Inappropriate comment? Wow, that's a stretch of the rules isn't it? Is it so inappropriate to detail techniques that have worked for me, even if they don't follow the acousticians rule book? Sensible discussion on parts of my post would have been helpful to others, but nope - just have a pop and cause me of long windedness? I tried to be helpful, and as detailed as I could to a fellow Brit. If the forum want short sound bite length posts that's a bit sad. Warning me in a message that I may be banned for the post is amazingly over the top as a response.

    I didn't realise that one criterion for posting here was absolute adherence to science, and public stoning for diverting from the truth as known to acousticians! There really was no reason to be so rude. You could have contacted me privately to explain, but no let's just say he knows nothing. Nice!
  6. Ramshackle

    Ramshackle Active Member

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