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Suggestions for soundproofing my semi?

Discussion in 'Home Cinema Building DIY' started by CooperUK, Dec 29, 2003.

  1. CooperUK

    CooperUK
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    The title says it all really. I live in a semi-detached house, where the lounge is next to my neighbour's lounge.

    I am tempted to go down the Wickes insulation panel + plasterboard route to cut down on the amount of sound that leaks through to them.

    They want to do the same as they are getting an AV kit (knew inviting them round to see my PJ in action was a good idea - they also seem far more sympathetic of late to noise I create!)

    Has anyone else been down this route - does it make enough of a difference to be worthwhile?

    If we both soundproof surely that would be good enough to crank the volume up a bit despite being physically linked.

    Let me know from your experiences if you could...

    Thanks

    Coop
     
  2. DJW

    DJW
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    Hi

    Check this out :- http://www.soundreduction.co.uk/

    For serious soundproofing you require supspended walls & ceilings !!

    The killer is the bass sound which travels via anything that is connected to your neighbours wall (eg. Ceiling joists).

    Saying all that I reckon insulated plasterboard only held in place by the top & bottom via flexible sealant (no screwing into battens etc) should do a fair job.

    Good luck

    Dave
     
  3. Gary Lightfoot

    Gary Lightfoot
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    Some good points there Dave. :)

    One of the methods often used to prevent sound transmission between party walls is relatively cheap and simple, and can be a DIY task if you're handy with a few tools.

    Using 4 x 2 wood, build a partition wall 1 inch in front of the existing wall (uprights at approx 600mm centres), and fill with 4ins of rockwool insualtion. This helps stop in-wall resonance and some of the higher frequencies. Then add two layers of plasterboard. As you've only attached the new wall to the floor, ceiling and side walls of your house, you can use screws to fix the boards into place. Make sure the second layer of plasterboard edges don't line up with the first. It's also a good idea to seal around all edges with a high modulus silicon rubber or similar.

    Using no more nails or similar will to make the wall rigid. A flexible wall can act as a bass trap and reduce the in-room bass considerably. Avoid resiliant bar for the same reason.

    Use silicon to seal around all edges before fitting skirting and coving. Where air can go, so can sound. As Dave has already said, bass is the real tricky problem, as it vibrates anything it touches. One way to reduce this is to use mass as a barrier, and double plasterboard acts as a good mass for this. As your new wall is touching your existing walls, some bass vibration will be transferred, but is reduced when limited to floor and ceiling apparently. The air gap also acts as an insulator for noise.

    As Dave has alluded too, for total isolation, a 'room within a room' is the perfect solution, but this means building a new floor on an isolating material such as rubber bungs or something like Wickes 30mm high density slabs (see pack for details!). You then build your 4 x 2 walls as described, and fit your ceiling to those. By removing the existing rooms plasterboard ceiling, you can gain some extra height. Double plasterboard again, with insulation above. The door can be a bit tricky, but if you're not too concerned with noise within your own house, then that doesn't have to be a consideration (though a heavy density door can help)

    I used the new wall theory but with a compromise with my loft - I used 2x1 studding and Wickes 30mm slabs with two layers of plasterboard for the rear wall, and the neighbours don't hear a thing. If you both intend insulating the same wall, you may get away with the 2x1 studding, 30mm slabs and two layers of plasterboard in each room. That way, neither of you loses too much room space (3.5 to 4ins each, instead of 6).

    IIRC, Smurfin did a similar thing with his garage door, and had great results, so it does appear to work very well. :)

    Gary.
     
  4. CooperUK

    CooperUK
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    Cheers for the advice there guys!

    One more question - what brand/type of flexible sealant or no nails should I use? Do I not use nails at all? Does 'no nails' type glue retain flexibility when it dries?

    How about if I used nails/screws to hold the plasterboard to battens on the existing walls, but with dense rubber washers to create flexibility? Or screw through a layer of the rockwool?

    The WF prevents taking up six inches of the room. I think I will only be able to get away with 2x1 battens and a layer of plasterboard (maybe two if I don't tell her ;) )

    Once again - thanks!
     
  5. Gary Lightfoot

    Gary Lightfoot
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    You don't want flexibility in the wall unless you want to absorb the bass from the room. The wall needs to be rigid. Placing some rubber spacers between the battons and the wall may work, but leaving a small gap will isolate better. You don't want to fix anything directly to the party wall.

    The rubber sealant or similar is merely there to prevent noise leaks through gaps from your room into next door. Daves suggestion of using the flexible rubber as the fixing will work very well as a way of reducing bass transmission, but that flexibility may also transform the wall into a huge diaphragm and bass trap.

    Any silicon rubber sealant will do the job, but if you're strapped for cash, then builders calk may do a reasonable job provided it keeps it's seal. You'll probably need a few tubes of the stuff to seal around the floor, walls and ceiling, and the caulk is around 99p a tube, but the silicon can be around £3 IIRC. I used B&Qs own brand No More Nails (gorget the name) as it came in boxes of 6 or 8, and was quite cheap.

    You can screw the first layer of plasterboard into the battons, then glue and screw the second layer (also screwing into the battons). The header and footer studs will be fixed to the floor and ceiling, and you fix the upright studs to those at 600mm centers. This wall should not touch the party wall.

    I'll try to find an image or pdf that I had which shows this in detail if that will help. There are some pics on my website which show how I made the wall in my loft. It's fixed to the floor and side rafters but doesn't touch the party wall.

    HTH

    Gary.
     
  6. buns

    buns
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    even if it doesnt help, this makes for interesting reading.

    ad
     
  7. Gary Lightfoot

    Gary Lightfoot
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    Great stuff - thanks Buns - that's similar to what I was after. :)

    The very first pic shows the studd wall, and this should be built away from the existing wall. Two layers of PBoard is better than one, Use the half inch type, or use one layer of half inch, and another layer of 5/8ths.

    The second pic shows a wall with resiliant channel - a great way to isolate, but also a great way to suck all the bass from the room if you're unlucky. You may need 4 or 5 Servo 15s to get any bass back. :)

    The third pic shows what you and your neighbour should do - except you have your existing party wall inbetween the two walls.

    If the 60db attenuation figure is accurate, then two layers of plasterboard will increase that, and as both of you are doing it, I guess that could mean over 120dbs of attenuation..

    HTH

    Gary.
     
  8. chirpychips

    chirpychips
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    I found www.domesticsoundproofing.co.uk to be very helpful. They have some nice flash diagrams explaining how to use neoprene on the back of battens, and how to use resilient bars, offset layers of plasterboard and soundproofing mats etc. Here's an example. I based my sound insulation on this (except I used Gyproc soundbloc plasterboard) and am pleased with the results......
     
  9. Gary Lightfoot

    Gary Lightfoot
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    Excellent link - though I wouldn't recommend using resiliant bar.

    It's brilliant for isolating a room, but can sometimes convert the walls they are in into bass traps. You could fit five Servo 15s in there and still not have enough bass.

    You may get away with it if you fit them, but if you do create bass problems, then the only way to resolve it is to remove the resiliant bar.

    Gary.
     
  10. chirpychips

    chirpychips
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    Yes - there has been some debate about resilient bars on various forums with respect to its impact on bass. Some time ago I sent this email to www.domesticsoundproofing.co.uk:

    Their response:

    In my room I have 1 Velodyne CHT-15 and there's plenty of bass to be heard (but not by my neighbours!) I did however use a floating floor - the builders put down several layers of rubber sheeting on which was constructed an isolated wooden floor, i.e., a floor system not fixed to the walls or concrete surface. In my case it was the bass causing the most problems with the neighbours so that's where we focussed our efforts....

    Best Wishes
    Chirpychips
     
  11. Gary Lightfoot

    Gary Lightfoot
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    You've certainly done your homework!

    Building your room on the rubber and having the new walls not touching the existing walls or ceiling effectively makes a room within a room, and is the ultimate in sound proofing - I'm impressed!

    So you went with the bar in the end I take it - had you had the original room up and running with the CHT-15, and if so, what did the new room sound like in comparison?

    Cheers.

    Gary.
     
  12. chirpychips

    chirpychips
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    Well that's a very good question Gary.

    Unfortunately it isn't a like for like comparison as the home cinema was moved from the living room down to the converted garage. But the bass has changed in quality - no doubt about it. It's still musical and can be "felt" (tingle in the air etc) but I've had to turn the volume up a little to make up for lost power (then again the new room is a bit longer and wider). I suppose using resileint bars can be viewed as a trade-off between sound insulation and a slight loss of bass power. My greatest fear was that it would become boomy but that's not a problem. I think it just has to work a little harder. But it's nice to have the volume up now without worrying about the time/neighbours. You know one fairly surprising thing is the importance of the sound insulation around the door leading to the hallway. And the amount of sound that can leak out of a key hole is incredible!!

    Regards
    Chirpychips
     
  13. Gary Lightfoot

    Gary Lightfoot
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    Hi Chirpy,

    Thanks for the info - room size definately has an impact on bass performance, so it's not cut and dried as to the reason for the slight loss, as it could be the size or resiliant bar. Either way, you've managed to get a good isolation without compromising the acoustics.

    I'll see if I can find the link from avs, but I seem to remember something about using two layers of plasterboard helping considerably, and is almost as good as a single layer with resiliant bar, but without the chance of the wall becoming a bass trap. I can't remember exactly, but I'll see what I can find for other people as a reference. I seem to remember that the Sound Transmission Coefficient (STC) for home theater walls should be 65, so I'll try to find the link for walls construction which shows what methods bring the best results.

    The amount of sound that can travel through small gaps is quite an amazing thing I have to agree, and one small hole can, as you mention, totaly negate any gains made elsewhere. I find using silicon rubber an excellent sealer for all edges and gaps.

    What did you use for your door, and how did you achieve a good seal?

    Gary.
     
  14. Gary Lightfoot

    Gary Lightfoot
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    Here's some data:

    2x4 insulated wall with RC and double dry wall* STC=52
    Stagger framed insulated (one layer) 2x4 studs, double drywall STC=53
    Stagger framed, 1 layer insulation, double dry wall both sides STC=55

    IIRC, Staggered frames refers to removing the existing plasterboard from a (4x2) stud wall then building the new 4x2 stud wall within the existing one (without them touching of course) - it reduces the amount of space the new wall takes up in the room.

    Here's a link about RC (can't find the original) which has two points of view:

    http://www.avsforum.com/avs-vb/showthread.php?postid=2889946#post2889946

    http://www.avsforum.com/avs-vb/show...=212438&perpage=20&highlight=stc&pagenumber=1

    Here's another where this is said:

    "I really should give some real STC numbers for some wall constructions. These are typical values and assume complete caulking. Your mileage may vary.

    Ordinary single stud wall - STC 35
    Add porous insulation inside cavity - STC 37
    Add a second drywall layer on one side - STC 40
    Add a second drywall layer on the other side - STC 45
    Add resilient channel - STC 55

    That's about as good as it gets for single stud construction. Double studs can yield an STC as high as 66."

    http://www.avsforum.com/avs-vb/showthread.php?postid=2889067#post2889067

    So it seems that staggered wall studs can achieve similar results as RB (my original comment was innacurate), but here in the UK we mostky have brick walls, so that should be interesting to see how they add to single stud RTC values.

    If anyone else wants to pop over to avs and find out how to do soundproofing properly, then use Dennis Erskine and Terry Montlick as names. Both know their subject very well, and although they sometimes have conflicting ideas, it'll give you a good guide how to go about it.

    HTH

    Gary.
     
  15. chirpychips

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    An interesting read there Gary. Thank you.

    I don't know exactly where the builders sourced the door seal from (I'll find out) but I do know that it is a commercial grade acoustic fire seal around all sides of the door (including the hinged side). It's made up of a brush and a rubber flap that seems to create a suction seal when the door is closed. It requires a bit of of a push to initially open the door. There's an angled strip of rubber around the door frame and a rubber flap around the door and the 2 create a good seal when the door is closed. As the room used to be a garage the door is a solid fire door. It has a keyhole below the handle which I filled in with some left over rockwool. I think at some point I will remove the handles, fill in the lock hole cavity with high density wood filler and buy some internal door handles instead. Incidentally for very little extra cost we had a triple glazed window made up for the room, rather than double glazed. Ideally I wanted the glass to be different widths but the glazing company couldn't do that within a reasonable budget - so I made do with three sheets of the same thickness.

    Cheers
    Shaun
     
  16. Gary Lightfoot

    Gary Lightfoot
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    Thanks for the door info Chirpy, looking forward to finding out the source was.

    The window thicknesses - is that for sound/insulation differences, or something else?

    Gary.
     
  17. DJW

    DJW
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    Also from memory I believe with Double /triple glazing you have a small gap between panes for heat retention, whilst for sound proofing you go for the larger gaps.
     

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