Adding a floating floor can dramatically increase your sound isolation because it disconnects the whole room structure from the rest of the building. This is especially necessary when isolation of low frequencies such as bass drums and bass amps is required.
There are two ways of floating a floor.
The floating timber floor is the more typical for a home studio whereas commercial studios (usually built in commercial buildings) usually opt for the floating concrete floor.
This consists of laying a double layer of 16mm (5/8") plywood or particle board flooring on 100 x 50 (4" x 2") joists that have neoprene pads placed at the points where the original flooring joists are. Rockwool is placed in the cavity between the joists to dampen any resonance.
FLOATING TIMBER FLOOR
Floating a concrete floor also gives excellent isolation. You can suspend the floor:
FLOATING CONCRETE FLOOR
As you can imagine the concrete compresses the fibreboard between the sheets of fibreglass and creates a multimedium isolation barrier. The concrete has a reinforcing steel mesh laid in it.
Don't forget to place your cable ducts in whatever floor structure you choose. There is nothing worse than cables all over the floor in a studio because they forgot to lay proper cable ducts. The ducts can be standard poly drain pipe or you can create a wide shallow duct in your formwork. It is advisable to run your power down one duct and your audio down another or split your one duct into two as shown.
When your cables go through walls make sure that you seal around them or all the work you put into creating a sealed room will be lost.