Yea.....those mods can not be done to this headset.
Passive is merely put something between your eardrum and the sound like earplugs, ear muffs, headset cups, etc...... just something that muffles sound.
Active noise reduction is an electronic system that senses a particular frequency....(usually the lower frequencies) and makes extra noise (white noise) that has the exact opposite wave. When you add the two sound waves, it strives to equal zero sound. (if an engine wave propogates 1 to -1, the ANR noise goes from -1 to 1 at the same time).....
If you try on an ANR unit with the ANR off, then turn it on you will hear a hissing sound which is the (white noise). When in the airplane it has a very noticeable effect.....try one out one day and you will understand.