"Party Voice"

On several occsasions when my dad has to travel for work, my mom will accompany him and leave me to take care of the home front. They of course call, nearly every day, to check in. On their most recent trip, my mother called and when I picked up she informed me I didn't have my "party voice" when I had answered. I responded that I didn't know what the hell a "party voice" was and she laughed it off. I guess I missed that joke. Then she preceeded to tell me my friends could sleep in the living room, in the event that they are unable to drive home. I raised an eyebrow to this one. I don't recall anyone I have over being unable to drive home. So now I'm curious to see what they think is happenening when they aren't here. I'm also curious what a "party voice" is if anyone can help me out.