Dublin has discovered his voice . . . EGADS!!!

Something I've learned about myself: apparently, the sound of my dog barking (not ANY dog, just MY dog) makes my blood pressure go THROUGH THE ROOF!  And now that Dublin has discovered his voice . . . oof!  How can I teach "quiet" (or something) so that he knows when to give it a rest?  
Right now he barks as we are preparing his food, but we play Mine and he's pretty quick about sitting and zipping it in order to be fed, but there are 2 or 3 random other times throughout the day where he just starts barking, barking, barking . . . it's never AT us, so that's good, but I have no idea why he's doing it, so I'm not sure how to prevent it, or motivate him to stop (does that make sense?).  I feel like just randomly rewarding him when he's being quiet is so abstract that he won't catch on to what behavior we're rewarding.
He's such a good boy, so sweet and goofy, LOL!  But oh that sound . . .
THANK YOU!!
Dublin's Mom