Active Noise Reduction Headsets - How they work

[Barnstormer1982]

Good afternoon fellow Private Phlyers,

I am looking for some technical background on the functioning of said ANR headsets. I've seen a graph in a German GA mag a couple of years ago where there were two sinusoids compensating each other, and now am just looking for such a graph on the web as a fried of mine wants to show this to his ground school class. I haven't been able to find it yet, does anyone have an idea?

Thanks for your help,
BS

[soay]

Sennheiser's description of how it works can be read here.

[Barnstormer1982]

brilliant - exactly what i was looking for.

thanks! (coming in chorus from groundschool folks)