I have two different mic's that I have plugged into my computer using the stereo/mic jack and both of them make some weird noises. When they are muted I can hear a faint electronic ringing sound as well as when I hold down a key on my keyboard I can hear a series of rapid noises through my headphones as well. Does anyone know what could be causing this? It only appears to be when my microphone is muted. Only other people can hear it too unless I activate Listen to this device.