I have a similar problem and still couldn't find a fix for it.
The sound that I hear is like a ringing or vibration.
I thought it was from the alternator pulley so I changed and and the alternator spring tensioner too.
What I observed is that after I changed the spring tensioner the sound seems to apper in a broader rpm range. So I deducted that it some component on the accesories belt that has a problem.
I hear this sound in any gear, when the engine is from 2000 to about 2500 rpm so at maximum engine torque.
It's more like a vibration.
I suspect the alternator rollers maybe or the powersteering pump rollers...
I'm not sure at all, many mechanics said different things, already invested in the alternator pulley and tensioner for nothing...
I will try to remove the accesories belt and run the car whitout it to see for sure if the noise is from the accesories belt. If it still appers then it may be from the timing belt or something else.