I actually had this problem when I first started and tried to use a headset. I actually addressed this in the podcast I just posted for pod-aware. I went through 2 headsets trying to get rid of the humming, and finally got a cheap stationary mic. I never found out why it does it. Other ppl with headsets have no problem, but the majority use a standing mic, so I wonder if the problem isn't that you're recording with the mic and that not what the mic is built for.