optimizing ceiling height?? Help!!

[shimmer]

Thanks Greg,

Sorry to hear your contractors are messing things up! Tell them to F**K off! No good work no money.

Thanks for the design. I'll have a decent look and see what I can come up with for my basement.

[Gregwor]

Tell them to F**K off! No good work no money.

The house builder company hires the contractors. I asked about firing them and getting different ones and I have no power. My situation sucks. Things will come to fruition soon and I can only pray that they install the HVAC and plumbing in such a way that I can make my design still work well.

Greg

[shimmer]

Hey Greg,

That sucks. If work is not done propperly someone nerds to take responsabilty! Contractor or house builder. Dont take that crap!!

One more question. In your design you have double silencers. One on the inner leaf and one on the Outer leaf. Is this necessary?? I Guess one on the inner leaf should do the job? Not?

Thanks!!

[Soundman2020]

...you have double silencers. One on the inner leaf and one on the Outer leaf. Is this necessary?? I Guess one on the inner leaf should do the job? Not?

If he did that, then there would be no isolation where the duct passes through the outer leaf... In other words, the wall cavity would be exposed to the outside world through nothing but the thin sheet metal of the duct...


- Stuart -

[Gregwor]

If he did that, then there would be no isolation where the duct passes through the outer leaf... In other words, the wall cavity would be exposed to the outside world through nothing but the thin sheet metal of the duct...

He's referring to if I didn't use a silencer at each leaf penetration.

Greg

[Soundman2020]

He's referring to if I didn't use a silencer at each leaf penetration.

Right. I got that. And if you didn't use a silencer, then the duct itself would pass directly through the leaf. Just a leaf with a hole in it, and the duct going through the hole. Thus, no isolation. All of the sounds that occur inside the wall cavity (such as the resonances, for example....) would penetrate through the thin sheet metal of the duct inside the cavity, pass along the duct, and exit through the thin sheet metal of the duct, out into the big wide world. Conversely, any sounds occurring out in the big wide world would penetrate the thin metal of the duct, move down the duct, and exit the duct inside the wally cavity, where they now only have ONE leave to deal with, in order to get into the room...

OK, so that's all hypothetical and simplified, but the effect is real. If you only isolate a duct where it passes through ONE leaf, then by definition you have NOT isolated it's passage trough the other leaf, and thus you have not isolated it. There's a clear path for sound to take through the duct, bypassing the leaf entirely.

The alternative is to make the "duct" very massive (eg, a couple of layers of MDF), connect it directly to the silencer on the inner leaf and have it pass clear across the cavity and out through the outer leaf without touching it (decoupled with something soft, eg: caulk, sorbothane, neoprene, etc.). That improves the situation yes, but you still don't have good isolation: you are limited by the mass of the walls on the single silence box, since that's all that remains between the outside world (beyond the outer leaf) and the inside world (in the room itself). This is better than just having a duct going through the leaf, but still falls far short of the isolation you would achieve with a silencer on each leaf.

That's what I was trying to say in my too-abbreviated response!

- Stuart -

[shimmer]

Allright, i cant build a silencer on the outside of my Outer leaf . Basement wall.

So If i build a silencer on the inside of My inner leaf and one on the inside of My Outer leaf, things should be ok right?

[Soundman2020]

So If i build a silencer on the inside of My inner leaf and one on the inside of My Outer leaf, things should be ok right?

Sure! The silencer itself can be on either side of the leaf, as long as it is there. Just take care to make sure it doesn't "bridge" the two leaves: no part of the silencer can touch the inner-leaf. (It's best if it isn't in contact with the outer leaf too, but that's not so easy to implement in practice)


- Stuart -

[shimmer]

Awesome im getting the idea.

TO the drawing board.

[Gregwor]

Right. I got that

Stuart, I was directing that at shimmer, not you hahaha

Greg