[D]

On Oct 16, 1:45 am, "Richard Crowley" wrote:
"D" wrote ...

A background (about 50hz) rumble appears in a sound from
microphone. Windows XP SP2.

In common use, "rumble" applies to low frequency *random noise*
such as from an air duct or a subway train or from a distant highway.

If you are hearing interference from your power mains (presumably
50Hz if you are posting from Russia), that is called "hum" and it is a
very *constant* tone.

We will assume that you mean that you are hearing interference
from power-line hum. If it is *rumble*, then it is acoustic and you
should be able to hear it with your ears, no headset, no computer.

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?

Does it hum when no headset is plugged in?
If so, then there is a problem with the computer or sound card.
If no, then *both* of your headsets have a problem

Does the hum change when you move the headset around
the room?

Does it hum when you try using a differen computer mic?

rcrowley posting from rec.audio.pro
Thanks Richard Crowley for your explanations!
It does not hum when no headset is plugged in.
One of the headsets is brand new and checked.
Yes, the hum changes when I move the headset around the room: the
further from the computer case the louder.
Yes, it hums when I try using a differen computer mic: both headsets.