Hi, I bought a frame off ebay , built it up, had it tuned by the LBS. Riding it for the first time, I found that going over rough pavement brought out a strange rattling sound. I thought maybe it was a bottle cage. Checked them they were tight. Tightened up the headset a bit, it got a little better but didn't go away.
There's no play in the headset, and it is quiet on smooth pavement.

I'm not sure what to try next.

The BB is new I installed it myself. It's an FSA isis with Bianchi team carbon cranks.Also brand new.