Your problem currently is using the "Wait" action, which basically breaks the normal flow of the event sheet.
A loop will run to completion in one frame.
A wait action will basically take what remains of the actions after it out of the current flow of events, and complete them at a later time.
In your loop, there are no actions after your wait, so nothing happens. All four instances of your sound get played in the same frame.
If you use waits, it is best to have all your actions in one event rather than a loop.