laptop - Processor noise

I have a Acer Laptop (Aspire E 17 E5-773G-715H if that matters) with an Intel Core i7-6500U and an NVIDIA GeForce 940M running Win 10 and I'm annoyed by processor noise made by that notebook.

The noise appears when the laptop is in "idle" state and disappears when I drag a window around or hold down a key while in a textfield.

I already checked everything and can say for sure that the noise does not come from the HDD (Because there is an SSD in it) and neither from the fan. It seems to come from the speaker.

I've recorded audio of the noise in a quiet environment: https://vocaroo.com/i/s0xpEOnqtJ8L (The noise isn't very loud, so you should turn up your volume. Yes, it's safe to listen to it in high volumes on Headphones, etc. No loud noises were made.)

I also already saw this question, which an approved answere were given, saying that it could be the power supply, which here isn't the case.

EDIT: I also tried to disable the main sound device to see if it would make a difference, which it sadly didn't.

Any possible workaround (or maybe even solution) to make it stop is highly appreciated.

Suggestions are also welcome, as they may lead to the solution afterwards.

Answer

Noise can come from a wide variety of components in a computer.

You say it is not a power supply but even in a laptop you do have power switching and regulating circuits that all can create physical and electronic noise. You need something to convert the battery voltage into the various voltages used by the system.

Chances are that under "idle" load one of switching regulators is switching down to a lower frequency and one of its harmonics is creating noise in the speaker wires.

Alternatively it could be something known as "coil whine" where an inductor in the switching regulator is vibrating at an audible frequency. The fact you can hear it is for the same reasons as the noise from the speaker, but is created by a different mechanism.

There isn't really much that you, as a user, can do about this. It is either a design issue or a sign of age though it is not a problem in the long term.

You might be able to go into the power plan options and raise the minimum CPU power level to prevent the CPU from entering its lowest power state which might in turn stop the audible whine, but obviously this would waste at least some small amount more power and thus reduce battery life slightly.