That depends on the distance -- it won't work for coworkers very close to you, but anyone more than a few meters (depending on volume) will be removed.

Though keep in mind that they remove noise, so things like fans are going to be gone, but they aren't made to shut everything out.

The QC's don't completely wash out background noise. If you listen to your music loud enough (which is probably too loud), you literally won't hear anything around you. But normal use, I find that it muffles outside voices enough not to get distracted, but not so much to the point where if someone says my name I can respond. An added plus, is people will bother you less if you're wearing them. Sometimes I like wearing them without listening to any music, just to create a quieter environment.

I do this too, sometimes I just don't want to listen to other people in the other.

On a plane I find that I can actually hear voices better, because the background of the plane is gone. I don’t believe people who say “noise canceling headphones”, because they just don’t work that way. You’d need both the headphones and music or something, and having to listen to music all day can be just as fatiguing.

I have been having this problem too

If you listen to music on normal volume while the noise cancellation is on, you can drown out anything.

I used to do that, and got tinnitus. Now, I try to keep the volume pretty low

Hm that sounds kind of worrying, but maybe we have different definitions of normal volume? I've been using noise cancelling headphones pretty much daily for 3 years and still no tinnitus in sight.

I also had some sinus issues that likely contributed. I really did have the headphones on for at least 8 hours a day. Then going home watching TV, not getting enough sleep. I'm guessing it all added up.

Sorry to hear that. Hope you're doing better now.

It depends on the distance from your co-workers, how loud they talk, and how much you are willing to damage your hearing to drown them out.

And also on your office's acoustics.

Agreed. And your office's arrangement/open-ness