I cannot hear the beep on my Zoji either, unless I am standing within a
yard or 2 of it.  So I timed the cycle while hovering near the machine. 
I found I could accomplish the same thing by setting a (LOUD) kitchen
timer as I punched the Start button.  Now I can add the raisins or nuts
or M & M's or whatever at 35 minutes and not worry about whether I can
hear the beep.  Sounds easier than taking the dough out, mixing the
raisins or cinnamon or whatever and placing it back in the baking pan.
John Firestone