Does anyone know what might be causing this sound? 

It only occurs when the engine is cold, and the outside temperature is cold (I'd say below 5 Celsius) 

I don't hear anything wrong there, mine is a bit noisy as-well when cold but not to worry as I consider normal 

It's like a whining noise. That tone that changes at 2s ( changed revs )

I don't worry about it, since it doesn't seem to affect the engine / car in any way, I was just curious what's happening.

Edited 19 January, 20224 yr by BogdanB