I hit one of L.A.'s famous potholes, which had been OVERfilled to the point of becoming a speedbump. So basically I was following a bus and didn't see and hit a speedbump at about 30mph. They said we needed the struts replaced. As for whether they replaced anything around them, I'm not sure. (My husband did the taking them in, getting it fixed). However: That being said, I think I heard this noise BEFORE the struts were replaced.
All of these are really good suggestions: if anything I've just added rules out something, please let me know. We tried taking it in to get a mechanic to listen to the sound, and ... no sound. It seems to occur only when we start driving in the morning. I first noticed it turning out of the parking spot sharply in the morning.