Ping noise in new exhaust system

I recently got my exhaust system replaced. After a drive (both long and short) and when I turn my ignition off the exhaust system under my car starts making a “ping” noise. Is this normal? Should I take it back to the mechanic who replaced the exhaust? What do I do?

Very common. The exhaust is contracting as it cools down, and some part is moving in relation to another part. It’s possible that a clamp or bolt is loose. Maybe the shop that installed it will give it a look-see for free.

Yes, and as a replacement it might have joints/clamps where the original had welds. Worth a check, but nothing to worry about.