At our office, we've recently moved to a shared workspace instead of individual offices, and part of the deal was that we each got a set of noise canceling headphones (PXC 300 from Sennheiser). I was skeptical, but figured pumping music directly into my ears coupled with the muffling effect of the actual headphones would be sufficiently "noise canceling". Oh, was I in for a surprise.
We finally got them today and I am impressed. Like not "yeah, they do make it quieter" impressed, but "holy <deleted>, it's like a <deleted>ing concert hall" impressed.
I use them (audio-technica quiet point) when I work at coffeeshops. When you put them on, you can actually hear the noise recede with a hiss. It is surprising.
However, it works to filter out concussive, deep noises and background roar the best. The odd result is that voices actually become clearer in the coffesshop.
That's fine when I'm in a conversation…but I'd like phones that block out all levels of noise, as in, complete, monastic silence. That would be productive.
I've dealt with an open office area for the last 7 years. Considered getting noise canceling headphones but I have to answer the phone occasionally. We just moved into a new office though and now I just close my door :-)