It may possibly be your timing chain or tensioner. I would take it to a mechanic soon to get a full diagnostic.
Check the heat shields on the exhaust system and catalytic converter. A lot of times, they rust and vibrate at certain RPMs.
It was just taken in for its maintenance check and the sound seemed to go away till we hit some bumpy roads. Heat shields aren't loose. It's a 2012 with 57,000 miles and garage kept.
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