Should my man's talking to himself be of concern?

My significant other is talking to himself all the time and its driving me crazy. Usually its when he seems to be upset. If the babies are crying, something doesn’t go the way he wants it, or whatever and then I’ll hear him not just make one or two comments but like a half hour later he can be in the shower or whatever and he is STILL talking to himself. Sometimes I hear swear words in these “conversations”. A few times I have said “I’m sorry were you talking to me?’ and he just says “no” like no big deal.
It’s kind of freaking me out. I fell asleep on the couch the other night with the baby(sick baby hard to get to sleep) and I heard my man walking thru the house talking to himself again and it sounds like angry words like “whatever” bullsh—” etc….
Our relationship is well- he is a nice man any other time but this is really weird and bothering me.ALSO-these are “conversations”-not just words you say when your mad.