Speaking to an audience of one.
HEALTH While silently reading a book, out loud you exclaim, "I can't believe she did that!" Perhaps you've chastised yourself while reconciling your checkbook, saying, "I should have carried the one." Many people tweet or blog to nonexistent audiences to give the illusion of speaking to someone else. Looking in a mirror have you asked, "Is that a gray hair?" These are just brief audible exclamations. Likely, you're not as bad as my friend who phones himself to leave voice messages as reminders — carrying on a conversation as though speaking to someone else — 'Jack, this is Jack. When I get home, can you remind me to phone Barbara and tell her to bring lasagna to the party on Saturday? OK, thanks. See you soon. Goodbye.'
Whether rehearsing a speech or memorizing a song, if you're honest, even you, to some degree, sometime in your life, have spoken while no one else was in the room. If you don't believe me, just ask yourself. While you confer on that, let's take a look at some statistics from a poll in which you are invited to participate.
Some people talk to themselves to relieve loneliness. According Linda Sapadin, Ph.D. of PsychCentral, it may also increase intelligence. Ambivalent thoughts are clarified so it's possible to take decisive action. Sapadin lists four types of personal discussions: complimentary, motivational, outer dialogue and goal-setting. 
On the other hand, if you are speaking to yourself and you hear voices telling you to harm yourself or others, or perhaps telling you to do things incongruent with reality, then this is unhealthy.  Seek appropriate help from therapists or a crisis hotline. You don't have to be alone.
If you are just a casual listener of your own audible thoughts, ask yourself, if you have a good reason not to be benefiting from A Bit More Healthy newsletter.