Question Laptop making high pitched sound when turned off.

[mixdix123]

Hi, I recently got a year old HP Elitebook 840 G7. It works perfectly fine, but I've noticed that after I turn the laptop off, it produces a very faint high-pitched sound followed by constant periodic high-pitched clicks. I can only hear the sound when i put my ear in the back of the laptops case and I noticed that the sound is probably produced from a location near the WWAN module (i didn't open the case, since my laptop has still one month of HP warranty, but I looked at online pictures of the internals and hence estimated the location of the sound). My question is could the cause of producing those sounds be something serious and should I take it to service, or is this a normal behavior of laptops. This sound persisted through the whole night when the laptop was off, and when it was not plugged into the wall.

 

[Grobe]

I guess that is power supply whine.