I don't know either, that's the term that my friend used, and he is a mechanic.

The sound is very prevalent when the car is idling. I can't say for sure if the noise goes away at high rpm. Even if the noise is still there, the regular engine and exhaust noise drowns it out so I wouldn't be able to tell. It's not the belt because I can see that the sound is coming from the engine, but it does sound similar to a sound that you would get from a problematic belt.