Things I Wish I'd Known Before Buying Noise-cancelling Headphones

I got some noise-cancelling headphones last spring — the Sennheiser Momentum 4 to be exact — and while I did do some cursory research into them, it turns out my knowledge was limited and I had some perhaps silly preconceptions. These revelations are based on my pair of Sennheisers, since I don't have any comparison, so it might be that I'm still out of the loop on some things. But here's some…