^Well, my experience recently is with the Civic and having put off replacing something that was known about before: the tie rods(outer specifically)
During the past 1-2 months it's been making a 'pop, pop, pop' noise, low speed and cornering(similar to CVs ironically which were replaced over a year ago). Almost as though it's in direct correlation to when there is torque(lower speed/gear) and it pulls at the wheels(FWD) where the tie rods are at, and the rods are popping somewhere near the wheel(perhaps the knuckle?).
I don't know how 'bad' they are but it's going in the shop tomorrow as I don't want to risk a wreck/seized up or steering failure. It didn't make sound before, but it's something that was known about.
On the other hand, your situation may/may not be anything. If it's something worth tracking down, you'd really need some method to try to find this sound. It seems like it only occurs while the vehicle is moving though. Try to simulate this and do so away from traffic, in a quiet area where you can hear more clearly and try listening with windows up/down. If it's something worth replacing, it will show it's ugly 'sound' more prominently(lets hope) before something does happen.
...or just relax and hope it's nothing.
EDIT: Great suggestion checking for things that may be loose exhaust wise etc and 'swaying' around; no direct reference to a sway bar mind you. He could have some old granny under the car trying to pick ax some precious metals away and cash them in for her spending money.