I'm building a home next year and am looking into ways to decreasing sound transmittance into bedrooms and playroom that sits above the kitchen/great room. Any materials that a reasonably priced that act in reducing sound to and from these rooms' walls and floors?

Rockwool insulation is often used for soundproofing, http://www.youtube.com/watch?v=WKk8h05GjYw. Using something to break the connection between studs and drywall would also be helpful, http://www.soundisolationcompany.com/index.php/solutions-products/soundproof-walls/stud-joist-isolation-gasket-tape

The three methods I am using are: Roxul sound insulation, sound channel and "Green Glue".
Roxul is rockwool insulation that goes between the studs, but sound channel and Green Glue are two methods that attempt to isolate the transmittance through the studs. Green Glue effectively requires you to double the sheetrock on the wall with a layer of resilient glue inbetween.
I have also seen double studwall methods used, particularly in Media Room applications that have big amplifiers contained within.

Hi Guys-

#1 Unless the mineral wool is super cheap, just use standard R13 fiberglass in the wall, R19 in the ceiling.

#2 The foam tapes do little to nothing. Other than extract cash from you.

#3 If the floors are going to be hardwood, they will dump vibration into the floor / ceiling joists. Consider installing the flooring on a mat forst. There are different ways to accomodate this.

#4 Double 5/8" drywall is a great bargain. Cheap and heavy.

#1 Unless the mineral wool is super cheap, just use standard R13 fiberglass in the wall, R19 in the ceiling.

Roxul (mineral wool) is a different thing from spun fiberglass. There is a reason it is specified other than just standard fiberglass.

#4 Double 5/8" drywall is a great bargain. Cheap and heavy.

As long as you have the ability to double the drywall, you will want to use the Green Glue to get the full benefit out of it.

I understand what mineral wool and fiberglass are. There is extensive lab data on this. Try IR 761 from the NRC of Canada. Finest acoustics lab in north America. The cheapest fiberglass available to you performs best in the low frequencies.

Do not be deceived by the name "green glue" it is not a glue and will not hold anything, it simply isolates compnents

You got that right!

Damping compounds take a few weeks to dry. After that the two sheets are together forever. Damping compounds convert vibration to heat

Staggered studs, insulation and "quiet rock" is what i did. With 3000 watts on each sub, and 2 five channel amps pushing up to 350 per channel, the sound transmission at my house is mostly vibrations throught the floor and roof.

Keep in mind that there are now 5 manufacturers of "soundproof" drywall. They are nearly all simply two sheets of standard drywall and a damping compound. Convenient, but very expensive per pound.

The heaviest wall will nearly always win, which is why double standard 5/8" drywall is so desirable.