A large portion of the home I'm designing/building has exposed timber joists from the first floor with 1.5" T&G exposed to below decking on top. I would like to minimize the noise between the upstairs and downstairs. Does anyone have any suggestions on how this can be achieved without an airspace as my design will not allow. I have heard of such options as a layer of homosote sandwhiched between the T&G and the subfloor but I'm not sure how this performs.

how much space do you have above the t&g?
-M.

1/2" to 1" is all I have so there is not adequate space for a 2x airspace.

With such a thin layer you may be limited to homasote or similar. I imagine there are some wonderful high tech materials out there for a price. I would search online for "sound proofing" and "building material"

I've used 1/2" sound board with good success (on walls). I imagine it would work fine on a floor between the two layers. It's cheap at about $8/4x8 sheet. I plan to use it on a floor for myself but won't be doing it for about 6 months. I don't imagine you'll be wanting to wait that long for feedback...

I wish I could wait but I will be building some of that floor over the next few days. When you say you have used "1/2" Sound Board" which product are you referring to: homasote? or another product out there?