Engine problem! Help please!

A couple of months ago a flying object (most likely a rock) bounced off the road and hit under my Hyundai Sonata while I was driving on the highway (around 80mph). When it happened, it sounded like the side of my car was hit, not under, so I checked the side and I saw no damage so I thought everything was okay. A few hours later, my engine stalled, which shocked me and when I looked under my car, I noticed I was leaking OIL. Apparently the rock punctured my oil pan and I had been leaking oil the whole time. I took my car to the dealership and they replaced my oil pan and fixed all the damage from the flying object. Thankfully, my engine was still able to run after the incident. They also did an extensive test on my engine and found no problem with it although they did report that it sounded much louder than usual.

My problem is that when I drive on the highway, my engine is much louder than it's supposed to be. I took my car to a different dealership and they also told me that nothing seemed wrong with my engine. However, there's obviously something wrong since my engine is so damn loud when I'm driving on the highway.

Does anyone know what could be the problem? What causes an engine to be so loud? THanks!

If two shops with access to the car can find no issues, online persons may not be able to help you.

My WAG is an exhaust that got repositioned by a lift, during the oil pan repair.

You will need to get a third shop to put it on a lift and then show them the noise.

Later,

most likely valvetrain dmage due to the loss of oil.
more than likely they can be fixed, and will not have to be replaced.