Soundproofing bedroom floor

[changenameagain555]

DS is in a bedroom in an extension to the existing house which has a plywood floor on joists (presumably common for more modern housing stock). The floor has a carpet with underlay. However, the garage underneath is very noisy. You can hear every bang that he makes (think feet and also sitting on and off (bouncing up and down) a wheelie chair when gaming. Has anyone successfully soundproofed a bedroom floor. Is decent acoustic underlay sufficient or do we need to take the plywood floor up and install something better? I don't think sound insulation (e.g. fibreglass) between the joists will help particularly as it isn't so much the speech noise which is a problem but the banging which I assume is as a result of direct contact between the floor and the joists.

F.

Airborne noise = insulation in the joists.
Impact noise (which is the problem here) = stopping vibration from transferring through the structure.

When I dealt with this, I lifted the floorboards and put in a dense acoustic board over a rubber isolation layer to add mass and break the direct contact with the joists. That was the only setup that actually reduced the heavy thuds.

For the materials, I used acoustic boards and rubber matting that I picked up from Online Insulation, and that combination has been good. The key is adding enough mass and creating a bit of separation in the floor build-up, otherwise impact noise just keeps travelling straight through.