Often it is a burst of sound.
Your speaker volume is set too high??
You dont really give much to go on. Try narrowing down the variables, such as other programs that are open, what are you working in in DW (code/split/designs)...etc etc..
speaker set at Medium volume.
when I came to this website, there was a burst of the system bell sound. Quick burst of few bells.
It happens in either code or design view. Sometimes, when I am deleting code with the delete key, but not necessarily so.
No other applications run at the same time.