Question Microphones going quiet and I'm unable to figure out why ?

[RatQueen]

I have two mics; a Blue Snowball, and one built into an HD Pro Webcam C920. Since October, both have begun exhibiting the same issue, where they are only just barely pick up my voice. Occasionally, and seemingly at random, they might return to proper functionality - only to drop back down to a whisper at a moment's notice.

I haven't the faintest idea how to troubleshoot this. Both devices worked properly on a friend's computer. I am unsure if it's an issue with my USB ports or something software related, but it's becoming very difficult to deal with. I would greatly appreciate any kind of advice.