Soundproofing Gone Wrong

hi i recently had a builder to put me up a doublewall for soundproofing .after he was done i recently stumbled across this website http://www.bobgolds.com/WallCharts/Q...bleLeafSTC.htm. now im getting a bit worried as my contruction worked out like this. sharedwall,airspace,stud,rockwool,double drywall then space,stud,rockwool,double drywall now im getting a bit worried as the picture is totaly different please can someone advise if this is going to do a good job or do i get them back to sort it out

[mattym]

that link dont work

sorry try the link again

[IronGiant]

Looks like you've got the double leaf STC 69 but with one set of drywall the other side of the rockwool, don't know if that would actually have any effect (might even be better!), but I doubt it's worth the upheaval of tearing it all down to find out. Who specced the build you or the builder?

[woody67]

Exactly what is the percieved problem?

There are many ways to construct a stud wall, did you give him a specifiaction to build to. If the wall is constructed properly then I can't see what grounds you will be able to call him back for.

Incidently, that site is american based so the figures may not be relevent in the UK. There are also many other ways to acheive comparable sound insulation without having such a thick wall

what are the other ways of acheving a soundproofed wall then

[woody67]

All walls have some soundproofing, and you have to think of what level of soundproofing is required.

Single or multiple layers of plasterboard, a layer or two of MDF, 4" instead of 3" timbers, denser quilt insulation, rubber or foam isolation pads, fabric surface finish etc.

It depends what you are tring to insulate from, the neighbours, the kids in bed, or the next room, or just to enhance the internal room sound. Is it for general sound or the lower frequencies from the sub?

If its just a typical wall for an HC, the 4" timbers, with 4" rockwool quilt, and one or two layers of 12.5 plasterboars and skim, will be adequate.

[Gary Lightfoot]

The STC (Sound Transmission Coefficent IIRC) is a universal standard as far as I know, but the figures shown in the link are all relative anyway. The best method is of course STC 69, though it sounds like you have an STC of 40 additional to whatever value the existing shared wall has (Add maybe 4 for that), plus approx an additional 6 for the two extra layers of plasterboard - one on each wall, (so maybe a total STC of 50). It's a common misconception that the construction of the STC 40 diagram should be better, but having a larger gap between the two new walls actually produces better results as the physical walls are further apart and the sound has further to travel from plasterboard to plasterboard so transmission is less (hence no PB on the wall faces facing each other).

That's not to say that you will not have an improvement in sound travel over the single wall though because you have, and I would think the sound reduction for most frequencies down to 125hz would be noticable.

Bass frequencies are far more difficult to tame though, and a room within a room is the best method in that respect I believe.

Gary.

[baldrick]

Obviously it's dependent on budget etc... but the optimal configuration for soundproofing is to use isolation so that the walls, ceiling and floor can all move indepently of each other and the superstructure of the room.

Doing this will absorb huge amounts of sound relative to other methods, especially those pesky bass frequencies.

[Gary Lightfoot]

A room within a room is the ideal, but you want the room to be isolated from the surroundings and not act as a huge bass trap, otherwise you could lose all of the sub bass from the room as well, and no matter how many subs you had, you'd not have any bass. Resiliant channel can have the same effect.

EDIT: assumed you meant all of the walls in the new room to be independant of the existing room as well as each other, so I was referring to the issue of floating walls acting as bass traps, but after re-reading, I think you meant the room within a room idea. If that's the case, I'll get me coat...

Gary.

[baldrick]

I was referencing to all surfaces 'floating'!

[Gary Lightfoot]

I wonder if that can be detrimental to in-room bass though - got any links for it Baldrick? What do you mean by 'floating' exactly?

Gary.

[baldrick]

http://www.customaudiodesigns.co.uk/...ofing/rbar.htm

[Gary Lightfoot]

The first thing I see there is resiliant channel - Aargh, don't use it for a home theater room because although it can do a tremendous job for sound isolation, it can also turn the room into a huge bass trap and you will have no bass at all. It's an unknown quantity so you can be taking a big chance with room response if you use it.

One example I use is from Dennis Erskine - one such room had used resiliant bar, 5 subwoofers and had no in-room bass. They had to strip down the walls and remove the bar (I assume they rebuilt using traditional methods). Once rebuilt, the room had one sub and plenty of bass.

I believe that the room should be built so that its audio response will be a known quantity (using RB won't give you that luxury), and then you should use room treatments to address any issues. Once that is done you can use equalisation to fine tune if needed.

Gary.

[Gary Lightfoot]

Here's a link to Dennis's post:

http://archive.avsforum.com/avs-vb/s...126#post125126

HTH

Gary.