Holding an out loud two way conversation to one's internal self is on a path to lunacy one is reinforcing that others will eventually be laughing at. But there are other ways to talk without doing so to an obvious others.
When performing a complex operation from written text (example product operation guide), especially those one will need to remember and repeat, it helps recall versus only visually reading words if one also verbally engages the vocal oral mouth muscles because that cross references memory across visual, control musculature, and aural neural areas. For example, while walking about in a supermarket, one reflects on the need to buy some sugar that is still many isles away. If one at that moment out loud simply softly blurts out SUGAR, it is more likely one will recall that minutes later versus just having kept that notion a subtle internal memory.
I sometimes blurt things out loud as though I am speaking with some emphasis and emotion to a group of possible others and not to myself inside. For example looking to the West, "Now that is an inspiring sunset!" Note within otherwise equal members of actual groups even a group of strangers, I do tend to be relatively naturally vocal confidently sounding like a leader. Or watching a tv football game at home alone when a touchdown occurs...TOUCHDOWN!
I also sometimes use a tiny micro-recorder to dictate thoughts to or perform descriptive narration when outdoors. This appears much like someone talking to someone else on a smartphone. Am not really listening but rather just speaking at the recorder in the same manner I might to another person. And it does take skill and practice to do so effectively.
I also readily talk to animals both pets or wild animals and at least I like to think, animals at times seem to react recognizing my body language and emotional vocal tones. Maybe because I grew up in a large family with pets. In my local neighborhood I've lived at over decades, crows and squirrels, seem to recognize me as a specific non-threatening human so allow my passage while keeping a wary eye just a couple steps distant.