Room acoustic question:OSB vs Plywood vs. gypsum-cement board subfloor?

AFter searching the archives for answers, I came up short. The older threads seem to deal with insulation rather than room acoustics.

Why do people recommend OSB vs. plywood for floating subfloor, besides the price? And what about cement reinforced gypsum floor boards?

My concerns are low freq absorbtion (room acoustics) as well as sound insulation.

My construction thoughts are (attic HT room above bedrooms - ceilings below are decoupled from joists):

1.
- wooden planks subfloor on the joists (cavities filled with rockwool)
- rubbermat 10 mm (~3/8") (isolgomma R10, european brand)
- (GG??)
- 1/2" wood
- GG
- 1/2" wood
- carpet

OR

2.
- wooden planks subfloor on the joists (cavities filled with rockwool)
- rubbermat 10 mm (~3/8") (isolgomma R10, european brand)
- (GG??)
- 1/2 " cement reinforced gypsum boards
- GG
- 1/2 " cement reinforced gypsum boards
- carpet

Thoughts on Gypsum vs. wood:
Gypsum boards are heavier thus better for low freq insulation, however also less flexible and therefor less absorbing (I think?). In other words, I might have an acoustic penalty for getting better sound insulation...?

Thoughts on OSB vs. plywood:
OSB is cheaper and a little heavier, thus better sound insulation; however, I read somewhere that the multiple layers in plywood creates better absorbtion and less low freq resonans, thus better low freq room acoustics...?

Thoughts on T&G OSB/plywood vs. non-T&G:
Using T&G osb/plywood makes it easier to lay vs. screwing the two layers of OSB/plywood together (GG in between) and using acoustic chalk to seal the seams. However, wouldn't it make the top layer (T&G) act as one big resonater rather than many smaller plates- and isn't that worse for room acoustics?

I appreciate any answer and help, but please state your knowledge level vs. hearsay (i.e. DE or BP answers will hold higher value to me )

Added:
My local wood supplier said today that he wouldn't recommend plywood for any kind of floating floor/subfloor, due to the tension in the wood. He said it would be difficult to control it - even if using T&G plywood. He recommended using chipboard as it is completely dead. Any thoughts on this is
Thanks!!!!

Jacob
Attic HT in progress

bump...
I have to lay the floor this week, so any help on this issue is really appriciated!

Jacob

Thanks for your reply
However, I think whatever solution I choose will be fine for sound insulation purposes. The heavier the layers the better.

However, I try to optimize the floor for inside room acoustics as well. And the word is that more or wrong kind of sound insulation can worsen your room acoustics. Concrete floor and walls as an example.
There I am thinking about the acoustic impact of material and construction:

=> Won't T&G OSB make each OSB layer act like basically one big sheet (rather than 12 smaller sheets)?
What will that do to the room acoustics vs. no T&G, 1/8" of space on all four sides between each 2' x 4' OSB sheet and acoustic sealant in this empty space.
Besides making the floor more stable, what will it do to the acoustics, theoretically?

I don't think the different solutions will be that different sound insulation wise, but I have a feeling the acoustic impact will be different.
So the question still is, FOR ROOM ACOUSTICS, why OSB vs. the two other materials? And what will T&G do for acoustics?

As for the raised floor option, I kind of have that already :-) Which is why I am not that worried about Sound insulation (only a bit - master bedroom is right underneath the subwoofer and action movies will often be with friends and not the wife )

Thanks a bunch

Jacob

Hi Ted,
OK, so basically it wont matter whether I use T&G OSB or not, since screwing the two layers together with GG between will make them act as one laminar layer anyway?

BY the way, how many screws should I use per 2' x 4' OSB board when having GG between layers?

Do you have any help on the in-room acoustic issues?

Thanks,
Jacob