Engine noise (not a tick) after highway speeds

[Obscenejesster]

So this is the second time I noticed this recently. I've only had this '16 for about 3 weeks. It has 20k miles on it.

 

The engine is pretty quiet at idle (cold and hot) with only the faint fuel injector tick.

 

After I drive on the highway for a 15+ miles, I notice my engine is slightly louder at idle. It's not a ticking noise. It's actually a very hard noise to subscribe but it's on the deeper side. It's consistent in rhythm. Best way I can subscribe it is "voom voom voom voom voom".

 

Anyone know why it only makes this sound after running on the highway for a while?

 

 

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