it was noticeable when standing outside as well. The sound came from the rear end of the exhaust. That's the way the engine was working at that moment, I'm pretty sure it was engine-related noise.

 

Sounds like ...exhaust
or a red herring

 

did you listen to the same video?..

lol

 

Sorry guys but I know a couple of you have high end home stereos systems and likely a 4 or 500+ dollar head set (Focal Azuyrs) and playback that video. While it may sound like something that should not be making any sound like that. It does not have the sound frequency response of exhaust. Playback and watching my Old school BSR EQ spectrum Analyzer

 

while I get you are trying your best to describe the sound and location, both are for the purpose of issues 2 different systems. Engine and then exhaust. So now if you say engine related that changes some thought process to wondering what the sound may be.

So I guess at this point either take it to a service shop so a ride along and point out the sound you hear or next step as a DIY is a complete scan of the ECU.

 

Sorry, for the confusion. By “engine-related,” I meant the engine was running in a mode that caused the weird exhaust sound.
It hasn’t happened again since then, but I’m still keeping an eye on it.

 

What’s the exhaust sound like when cylinders are deactivated?

 

Maybe next time if you can do a video at the area, you hear it outside the vehcle and don't move around.
Sorry I truly dislike cell phone video's getting about 1/3 our service customers that bring them to me all the time. I always listen and tell them thank you. But I never log that on the service write up.

 

Thats a great thought but on or off the video posted would not because that sound at least the way it was recorded in the video.
I do know where you are going with that but there is no other indication from the OP that would have caused his mystery noise.

 

Pretty good explanation. I hear the same thing. I recorded my own 2.5 of a different year and does not sound like that cold or warm.