This is an easy solution to get rid of static and humming noise from your microphone/headset. All you have to do is unplug your power cable. I am using a laptop so all I have to do is unplug the cable from the back. The static and humming will be gone. The reason for this is because your computer isn't grounded. Most laptop power cords have two prongs. That means it doesn't have that third prong, which is the ground prong. You can look up ways to ground your laptop so you don't have to unplug the power cord every time you want to use your microphone.
I found another solution to this problem. If you have a two-prong power plug that both have the same sized plug (not the one with the bigger left prong), try turning the plug upside down and plug it back into the socket. This worked for me. I found out about this here: http://forum.audacityteam.org/viewtopic.php?f=26&t=4769