AKG AV100 hissing sound normal?

Today I tried out my new AKG Av100 ANR headset for the first time. I am a very low time student pilot so I don't have any experience with headsets. There is a definite hissing sound when the ANR is switched on. Is this common with all ANR headsets or just the AKG's? The only other ANR I've worn was in Vlad's plane and only for 15 minutes. I was too excited to be in an RV for the first time and can't recall how his Bose were except that I thought they were very quiet. These AKG's are super comfortable though. Loved wearing them except for the hissing.

I went through two sets, both were far below my previous Zulu's in sound quality. Returned the warranty set for refund. Very comfy, but the sound quality and volume was far below my original Zulus. Unfortunate and hopefully they have fixed the issues I experienced.