When you have several of the 4 "Beep on Message" options enabled, especially for "Buffer", it can sometimes be hard to track down exactly where the ding sound is coming from. Sometimes it's caused by simply having some slow-volume channel not scrolled all the way to the bottom. Or, if you have event-beeps defined as a single beep as used for 'beep on message', then that could be the cause instead.
For scriptors, something like an identifier returning the $target aka $active window where the beep originated would make it easier to find the source. This would be an identifier similar in scope to $readn $flinen where the same result can remain for a long time.
For non-scriptors, probably the best solution would be also adding some text in the dialog right below the 'Beep on Message' box giving the $network and $window() name of the most recent ding beep would be helpful.
The text label would vary, depending on whether this would be something that updates in real-time while the window is open, or whether it just shows the value as of when the alt+O options tree was opened
Or, this could even be a good candidate for people to add to a popups menus like "go to latest 'beep on message'.