I think the voice registers you immediately, esp if you have some foolish sounding tenderly endearing chicky call you’ve been using since day one, and are most likely carrying food.I talk to mine as I approach, I figure that gets them over any changes to my clothes or whatnot. Though they all ran like hell when I carried in a windsock I was installing, and the wind sent it flapping...

Though seriously, it stands to reason the birds would react to something large and unfamiliar as part of their defense mechanism. Squawk, run for cover, then figure it out later.