There is obviously an opportunity for further research into noise cancelling, this time at the lower frequencies. You put a big sub in your house, a smaller sub in your neighbors house, and use the smaller sub to cancel out leaked bass from your place.

If only someone made a subwoofer with a built-in DSP. Oh wait...

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8