My car occasionally makes the same noise too, so I decided to check the strut nuts as well. I tried to wiggle the bar and it felt tight. I then checked the nuts with my fingers and they were not crazy loose. Finally, I set my torque wrench to 12 ft/lb and started with the driver side nuts and sure enough they were loose. Unfortunately, one of the bolts snapped on the third quarter turn
I checked the rest of the bolts and they all felt similarly loose, but I didn't perform more than one quarter turn on each because I was afraid of snapping another bolt.
Now that I'm missing one bolt I wonder if the noise will occur more often? In the mean time, I need to look for stronger bolts.