Perhaps the use of paradox is in order here. People generally can't hear you when they are walking away from you. Confronting someone acting like a clown says more about you than them. I recommend you use paradox and challenge them to act less professional. This approach takes practice so be patient. Who says clowns can't be professional and professionals can't be clowns? Jay Tatum

challenges we have day-to-day
what makes us winners in our field

here is one, you are a professional and one office over is a person that acts like a clown; they are smart and have lots of business, but how do you get them to act more professional