That doesn't sound like a situation where you're using the mic. Its not white noise, its a buzzing sound whenever the mic pics up your voice for transmission.
its been a topic in astro support forums for years and also amazon reviews:
I experienced it in every single a50 I've tried regardless of firmware and gen.
My opinion? Nope. After researching a bit over the past couple weeks, I narrowed my options down to two main contenders, with my cash going to whichever went on sale today.
Neither was on sale at BB, so, for me, those sales weren't good enough.
Luckily, Amazon came through with $75 off the Astro A50's.
I use this bad boy. It is pretty expensive, but the quality is outstanding, the comfort is perfect, and the psudo-surround is great. I can hear those guys coming up from behind me.
The thing I like is I have a gigantic head so they don't feel like they are squeezing my head.
http://www.amazon.com/dp/B00NY5ZP62
http://www.amazon.com/dp/B00MNPDMEQ
Both of which at 7.1 which was covered in at least the first post I linked.