Since this is a thread about barking and not roaming Ill answer the barking question.
If its the one that sounds really strange and drawn out, like of like a huffing bark (Ive heard squirrels make it too). It almost sound like weird bird? Anyway, It is not a fear sign. I suspect it might be a call to let other chins know his/her location. I know my girl used to do this call all the time till I got her a friend. She still will do it, but now its rare and in her sleep. The new chin will run up to her immediately and touch her nose, and she calms down. Try grooming his face chin style when she makes this noise and see if he calms down.
PS be cause I cant resist, I let my first chin roam while I did home work, He made a hole in the sheetrock when we werent looking and we had to carefully dig him out of the wall. So at the very least daily check the walls behind things like ur dresser and bed. I had him for about 2 years, on day while roaming he got out a small hole in a window screen (the window was 5 ft up so I haddent thought much about it). I was only out of my room for 15 min and he was gone forever. becareful. =( that was 14 years ago, I will never out grow my regret and guilt.