Welcome to the forums, newcomer!
Are you sure that the mic isn't brushing up against his shirt or jacket's zipper near his neck line? I'm assuming the headset your friend is working with has an inline mic. For this reason, we advise users to sate their specs to their issue to rule out any assumptions on our end.
If you will, list the specs to your build alongside your audio equipment as well as the headset your friend is working with. It's possible that your audio drivers might need reinstalling.