Could be chain slap, or it could be that you pause then engage the pedals in the process of going over bumps. Both are common, and it calls for diagnosis by ear, and tracking what's happening.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.