I got my answer!
The AppleCare guys were the ones who helped here -- the first thing they had me do was go to System Preferences > Users > [me], and remove all the LOGIN ITEMS.
There, I noticed the application "ChronoSync Background Scheduler," which I'd installed a few months ago. When I went to check the preferences for ChronoSync, it indeed was set to run in the background at all times, syncing certain folders with each other *every hour*. Furthermore, *-AND HERE'S THE CULPRIT-*, it was also set to make a Basso sound "On Failure." Now, since one of those folders no longer exists, it was indeed "failing" on the hour, every hour...Thus acting, inadvertently, as the Mystery Cuckoo Clock of Obnoxiousness.
So definitely check your Login Items and delete them. I hope this helps!
M.