Dog Barks at Company

Does anyone have any tips?

I sometimes tell him, "It's okay" but he doesn't believe me.

Other times, I smack a magazine on the counter, the loud noise grabs
his attention, then I say emphatically NO.

Thanks

I have a 3 year old lab who does the same thing until she has a chance
to be around them for a few minutes to either figure out who they are
or realize there is no threat. I have started putting her in my office
with the door shut and I then let her out once the comany has settled
in or has left depending on who the company is and how long they are
staying. I hope this helps.