Treating Floor in New Construction - Reducing Footfall and Vibration

Carpet? Carpet pad? Your're thinking wall to wall carpet right?
I did cork flooring in my basement listening room @ $3.29 PSF from Lumber Liquidators + installation (you can do it yourself in about a day).
I laid a black moisture barrier over the cement floor & then the cork flooring.
1,000 SF cost me around $5K with tax, delivery & moisture pad- Wall to wall carpeting would have cost me around $3K & I would probably be replacing it now.
It's soft, quiet, very durable (25 year warrantee) & wont have to be replaced every 5-7 years.
It's also a "green" product.
BTW - It looks fantastic!

Actually I am considering putting hardwood on the front (speaker end) ten feet of the room and carpet on the remaining 19 ft.

I have considered taking a hard look at cork; what brand/type did you use?  I have read that cork has good sound characteristics but that it is very soft and hence easy to damage.

Making floor joists deeper than necessary for the span, and/or shorter, will do more to increase stiffness than adding more joists, although 12 inches oc will not hurt in your listening room since there would be less opportunity for speakers and heavy equipment to not be fully positioned over joists.  Proper lateral bracing is also important.

let us know what your engineer says.

Stickman - One thing that I know for sure will stiffen a floor is to use good quality ply wood, glued directly to the joists.

The houses in our development were built with that cheapo board made from large flakes of wood. 

When I upgraded my kitchen I put reinforcing beams in the basement because we were putting ceramic floors down and I wanted to prevent bouncing.cracking - it worked somewhat.

Then I helped my neighbour replace a high traffic section of his kitchen floor - we ripped up the old floor and replaced it with quality plywood glued directly to the joists

The difference was amazing - his floor is like concrete (i.e. by comparison)

Both houses have joists at 12" centres

Hope that helps

I am thinking floor joists on 12" centers are a idefinite requirement.   I am not sure what the building code requires but since the room is fairly large at 22' x 29', 12" centers would seem reasonable.

I don't care for the OSB subflooring myself, so I will discuss with my builder the possibillity of using good quality 3/4 plywood.  Gluing the subfloor sounds reasonable also.