There´s a way to do it, but i don´t think you guys would like it. For strong sound reinforcement, there is a need for sound acoustics to be placed. Means couple of layers of diiferent materials have to be placed over on the floors. Including the windows, walls etc. It´s too deep a topic and the easiest way around it is to hire an acoustic contractor(professional one!) to reconstruct the room, would costly i think $15000 if i´m not wrong.
The other way is to read into Sound Acoustics yourself and get the materials, it would be cheaper but hell!! Anyway or the other, EDB approval has to be gotten i think.
Mattresses and carpets are some common layman methods, these materials absorb sound. Cover the room with all absorbing materials like books, curtains etc would help, but it´s be very hot. However, these are not sure ways to really deplete the sound travelling out of the room.
The final way i think is the best!!! Get an electronic drumset!!