No can do, Kit. First, you have to make sure the sound is contained within the room (you might as well soundproof the room) to be able to control it. Second, the noise coming in should be not an erratic or intermittent one. It has to be predictable for the DSP controller to sample it. Third, you would need a lot of mics, speakers, DSPs and computers to make this thing work. In reality, this, in essence, is active noise cancellation. Been done. Being done in airplanes to put down engine noise in cabins. Done in some auditoriums and acoustic spaces that need soundproofing but cannot do any physical touch ups because of historical importance (like castles, some churches, etc.). The process will be more expensive than soundproofing the room. Unless you can come up with something else. Then, you make money.