At the risk of drawing a common sense penalty from shane, if the person who is annoyed by the check six's, they could go into their sounds folder and rename/remove the sound file. Then they would only have to put up with the text in the system buffer.
Alternatively, for those who don't want a check six, I hear the knights are the place to be.
Alternatively for the ones getting an earful for giving check sixes inadvertantly, do something similiar to nopoops wall of butts -- make a list near the old virtual cockpit and mark down those who don't wish to get the check six calls.