I have no idea, but I create a frienzy here when I say "Hi booooys!!" and all 6 in the Martins cages go crazy haha Bobby goes nuts when I say bubbers, and Chuck puffs up and acts all tough when I call him Chuckers!
It's not your voice, it's the minute you enter the room and they smell you, then when you come close and talk to them gets them even more excited. A lot of people can't seem to understand that rats love humans. Just like dogs, most can't wait to be with you.