I have a feeling that the most promising solution would be in working out some kind of deal with your son, but here's an alternative -- maybe for while you're negotiating, maybe to make the final deal easier on you:

Noise-cancelling headphones. A friend gave me a pair when I was complaining about my noisy neighbors. They work surprisingly well. They were apparently first developed for airplane passengers, to cancel out engine sounds, passenger conversations and crying babies. They're battery-powered. You can switch them on without plugging them in, just to reduce ambient noise; plug them in without switching them on just to listen to music or TV; or plug them in and switch them on to listen to music (amplified considerably) with noise cancellation. They certainly won't eliminate the sound of drums being played in the same room but they'll cut it down considerably even then, and they may be enough to suppress farther-away drumming almost completely. The fancier ones cost a few hundred dollars but you can get an adequate pair for a lot less. Amazon carries them, among others.

Good luck!