OCIA.net takes a look at the Logitech SilentSound Noise Canceling Headphones in their latest review

As the description suggests, there is actually some active science/technology behind how the headphones function. Using Logitech's SilentSound technology, the headphones dynamically adjust to and filter out surrounding noise, leaving you with a quieter environment in which to enjoy your music. Logitech claims their headphones cancel out up to 22 decibels of noise - pretty impressive. This is my first time trying any type of noise canceling headphones so it will be interesting to see if this technology actually works or is just a clever marketing ploy.

Logitech SilentSound Noise Canceling Headphones Review