Looking at some of the reviews, it sounds like this hardware has its limitations, namely that it does a poor job of blocking out sounds in the frequency of human voices, which is the main thing that jhandl seems to be looking for.
"you cannot hear what anyone is saying unless they shout, and even then, it is difficult to understand them." http://www.amazon.com/review/R20X9DNAJC9ZX3/
"I use to study while my 2 year old screams her head off (as long as someone else is watching her of course!)." http://www.amazon.com/review/R29TUUYEQY98W9/
"I use them while doing research in a library. It's unbroken silence despite screaming kids and adults talking into their cellphones. People no longer understand proper behavior in a library, but I don't care. I can't hear them. It's wonderful." http://www.amazon.com/review/RQBNEZ9CX3O19/