Do you mean a beep every time someone types a character? I'm not sure there is anything to be done about the speed but if you describe why you want to do this, there might be an alternative solution.
It is a lab. So they are looking at a screen and counting. Once they get to a 100 we want an audible beep, so they know where they are. The iOS beep (FM Script step "BEEP") is to soft even with the volume all the way up. So we tried an audio file. That is way to slow, but can be loud. They are at count 108 by the time it sounds.