Anyone Else having this problem????

[MeggiemobileSFLA]

Ok, so i thought i had the problem solved and that the noise was normal but after hearing it again today im paranoid.... It only happens when i put my car in reverse and then into drive and accelerate that first time, i hear a ta-ting noise. The noise happens only once and doesnt seem to do it when im backed in and do not need to put it in reverse to get it into drive. The only way to describe the noise is to compare it to something like a rock or pebble striking something metal from underneath the car. I got so disgruntled thinking about it ALL day at work that i made an appointment with the dealership servive dept already for this weekend. Hopefully it's just something that can be fine tuned or adjusted but i will die if it's something serious. Why would a week old car do that!!!!!!! Im going crazy please help

Meghan