[D]

Hello!
A background (about 50hz) rumble appears in a sound from microphone.
Windows XP SP2.
I tried two headsets (which surely are good). The rumble decreases if
I touch the computer case. I checked the inside of the case, did not
find any improper contacts. The sound card is Creative sound blaster
live ct4830. I tried the latest Microsoft and Creative drivers. The
Creative driver does not output sound from microphone to speakers at
the same time, but only from a recording from the microphone. How to
prevent the rumble?
Best regards,
Dima