Need advice on a really annoying dog

I work at a kennel and there's this dog that just stands there and barks at me the ENTIRE time we're out in the play/potty yard. It's not just me, he barks at who ever is working the kennels at the time.

He doesn't bark inside, he likes people and likes being pet but when we're out in the yard, he stands a few feet from you facing you and just barks the whole time, standing in one position. If you put your hand out, he comes over to be pet but when he gets tired of that, apparently, goes back to barking.

I've tried telling him no. I've tried ignoring him the whole time, being consistent, but nothing works.

I wear earplugs but it's still loud and extremely annoying.

Any ideas?