Communication system front to back seat

Riding in my 2013 Flex I realized that the people in the back seats could not hear me talk unless I turned around and raised my voice.  Idea would be to add passenger speakers that could be activated or deactivated by the driver/front seat passenger that would send the sound (discussion) to the back seats to improve hearing between front and back seats.  Sound seems to travel forward well not sure need a back to front system.