Sennheiser PXC 250 Consumer Headphones

For low volume levels (which is where I want to use them), the headphones (with noise reduction engaged) have very nice sound. Turning the noise suppression off and on is amazing. I would have said that my office was quiet as a tomb. It turns out I was just tuning out an amazing amount of machine hum and similar noise. With the suppression on, I can comfortably hear that would otherwise be lost in the background.

Ignore the ads that talk about these blocking out people talking. They reduce that sort of noise as well as most headphones, which is pretty limited. Where they shine is in the sort of rumble and roar you get on trains, planes, and (surprisingly) in offices.