Bose (and other NC headphones) can only cancel repetitive noise. It can only send an opposite sound wave at the right amplitude and frequency at the right time

Bose (and other NC headphones) can only cancel repetitive noise. It can only send an opposite sound wave at the right amplitude and frequency at the right time to cancel another if it knows ahead of time what to send out. So airplane noise, traffic, airconditioning, servers whirring. I find that in airplanes it actually allows me to hear the cabin attendants better, as the drone is cut, but the voices are not. It's why they are not that great a solution in an open office. The isolation you are looking for you can achieve with ear defenders. Put them over in ear headphones, and you won't hear anything else but your music.