John Sayers' Recording Studio Design Forum Archive

excuse my english in the subject but I found no other way of saying it
i have room in the basement which im gonna try to make as sound proof as possible...I have neighbours on one side which I dont want to disturb too much. I think I know the basics of making a sound proof wall...I've studied some of the posts here. the problem I see is that there are lots of pipes (water, heating etc) that run across the ceiling (see picture). I thought it would be nice to cover these pipes with some kind of simple construction thats a bit soundproofing. I'm afraid that some of the sound will travel through that construction and make my "heavy" isolating wall less sufficent. I've come up with two alternatives:
A - I put the "heavy" isolating wall right on top of the existing wall. The problem with alt A is that there are pipes which doesnt make it possible to build the wall all the way to the ceiling. Also the ventilation is there making it more difficult.
B - I put the "heavy" isolating wall futher away and make a tiny room that can also be useful for storing stuff. A door has to be built in this case. I guess I need some kind of opening for ventilation also...since Im not gonna spend too much time in the tiny room I feel a bit confused at the moment...any ideas on what's the best solution in this case?

You didn't mention whether that concrete wall between you and the neighbor is solid concrete or hollow concrete block - if it's hollow, then your best isolation would be to add layers of mass (like gypsum wallboard) placed AGAINST the blocks, with no air space whatever. This is because hollow blocks act as a mass-air-mass system all by themselves, so adding another air gap and more mass will actually HURT your isolation at lower frequencies.

If the wall is of hollow block, this can be a real problem to figure out what to do about the pipes.

If the concrete is SOLID, then you would want to space a second mass (like 2 or 3 layers of wallboard on a separate frame) a few inches away from the concrete; this will make a good mass-air-mass barrier, especially if you take care NOT to allow the new frame to be in hard contact with both the floor AND ceiling; you would need some sort of resilient sway bracing at the top of the wall, along with total hermetic sealing at all joints.

If you build a wall out far enough to make a small room, the added door will reduce the isolation quite a bit; it's really difficult to make doors that seal well, and this can cost you 10-15 dB of isolation in some cases... Steve

thanks for the advice...I'll check out the wall.

okey I've heard that its just a wall of mortar with an air gap in the middle. something like 3 layers of gypsum right on the wall is the best I can do then I guess? or maybe 2 layers of gypsum and 1 layer of some other wallboard?

Yes, if there's already an air gap then adding more mass is your best bet; make sure each layer is hermeticaly sealed (caulked) with acoustic rated or butyl caulk.

Mass is your friend here - but if you put up multiple layers on the wall, you'd get a bit better results by only gluing strips every 400mm or so - this allows each layer to act on its own but doesn't add any more air gaps... Steve

but if you put up multiple layers on the wall, you'd get a bit better results by only gluing strips every 400mm or so - this allows each layer to act on its own but doesn't add any more air gaps

okey...what kind of strips do you mean? is there a post here on the forum which describes this in more detail? many thanks!

Sorry for the delay; too many projects seems to be my life story -

What I meant was, rather than gluing wallboard with full surface glue, you can get a bit better isolation by only gluing stripes between the layers so each layer acts on its own; this extra flexing expends a bit more energy, letting less through the wall.

This can be done by putting vertical stripes of glue in the same locations that wood frame studs would normally go - about every 600mm. Each stripe should be 75-100mm wide, and successive layers should have their stripes in the same location (but each layer's panels should have their EDGES in different locations for better sealing)

YOu will need to check locally for what types of Construction Adhesives are available; choose one that's rated for drywall but is not too "heavy-bodied" or thick; the panels need to be pressed FIRMLY against the wall when gluing, and held until the glue sets (not usually an easy job)

HTH... Steve

okey I shall give it a try. thanks steve!