Time for an inspection at a tire and alignment shop. Your mechanic would have inspected the car for loose parts before aligning it, but not necessarily for noises unless he knew to do so.
There is a tool you might be able to borrow or rent from an auto parts store that borrows them called the "Chassis Ear". It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Be aware that many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises.
What city are you in or near?
Saturday, March 9th, 2013 AT 7:00 AM