You are not required BUT this is one situation where I think you should quickly and calmly notify any LEO conducting a traffic stop. By notifying, it has been my experience, you may get favorable treatment and a speedier release for whatever reason the stop was initiated. By not notifying, it has been my experience, the LEO becomes edgy (had a NCHP officer draw on me and order me from the vehicle in daylight due to a firearm in plain view years ago) and once they discover it on their own they want to "see" (run the numbers) it and usually start a long fishing expedition.
I see no benefit for not informing on an official contact. On a public contact (ie. one where they contact you about something that does not involve you directly) I will inform concealed but not open. One a casual contact (you know them or say hello in passing) I inform them of nothing.
OASN, Steve I forgot about you yesterday. I was going to call you and see if you wanted to meet up and go to the gun show. Maybe next month if you are interested. I picked up a pistol and a pistol caliber carbine yesterday. Check the CVN armory later for pics.