Why do laptops make a faint, high frequency buzz when you call for CPU task?

[NeoPTLD]

I'm using a rental laptop from the school library. I noticed that when I do something such as minimizing and maximizing window, I can hear faint, high frequency buzz from under the keyboard. There is no drive access when I do this. I know that CPU changes in clock speed to save power, but I'm connected to AC adapter and even if it changed speed, we're talking about hundreds of MHz, well outside of audible range.

What's this sound from?

 

[Frightcrawler]

Are you blocking the ventilation holes?

 

[Zepper]

Perhaps there is a small fan in there that changes speed with load/temp.
.bh.

 

[jwwrs]

Neo,

This may sound crazy, but when I was a lot younger(in my thirties) I could hear High frequencies well outside the normal range. This included floresent lighting fixtures. I'm an electrician and when I would be in a room with variable frequency drives, I would have to wear earplugs.

As part of a pre-job physical, I had to have my hearing checked. They were kinda freaked and kept me in the booth about 15 minutes longer than usual. When I finished, they told me they had never tested anyone with that high of a frequency capability.

I'm in my fifties now and alas, my hearing is pretty much the norm with my age.

My ramblings are only to point out that it might be YOU and not the notebook.

jwwrs

 

[Bassyhead]

Does this only occur with that laptop alone? Perhaps it has something to do with something that drives the LCD.

Jwwrs: I wear hearing aids and they pick up ultrasonic frequencies