Basso alert keeps sounding

I've got a weird problem where my MacBook Pro keeps sounding the Basso sound as an alert or notification, but for the life of me I don't have any idea what it's for.

At first I thought it was Calendar or Fantastical, then possibly Mail, so I shut off notifications for all three apps. Nonetheless, the persistent Basso sounds keeps going off.

Is there any way to find out what applications use what sounds? I kind of remember that you could do this under Sounds many versions ago of OS X, but maybe I'm mistaken.