Satellite Pro S300L-105 - Whistle when power supply is removed

Question

I recently bought a Satellite Pro S300L-105, it works normally except that it produces a slight, pointed whistle, witch can be heard when the power supply is removed. After less than 10 minutes using, I feel pain to my ears and brain and it becomes unusable.
I do not have any hearing problem or so. and I've never had such a problem when using any other computer.
What is it due to, and what can the manufacturer do for me?

Answer 1

Hi
Very common problem with all sorts of electronic equipment.
The whistle is caused by the high frequencies used by switch mode power supplies. It's a bit like a car where you have a rattle that happens only at certain speeds, and that speed creates a certain frequency that resonates with something in the car that then makes a noise. The same thing happens in the power supply.
When you remove the power the laptop enters a different power mode and starts running things on a lower voltage to save the battery power, and the way the power supply does this is by changing the frequency the power supply runs at. This frequency is just right to cause something to start vibrating within it, and as the frequencies are very high, you get a high frequency squeal. It may be so high in frequency other people can't hear it, which can be a problem when support or the shop are checking are it if you take it back.
Just like a car with a rattle, not every car of the same type will have the problem and the same goes for laptops. Someone may have a squeal only when on mains power for example, or only when the back light is on full or on dim, or they just don't notice it.
The manufacturers do a lot to try and dampen down anything that might vibrate and squeal but are not always successful.
You might find turning off power management settings help as the power supply is then forced to supply more power and so the frequency shifts to one that doesn't cause a squeal, but then you will find battery power doesn't last as long.
It could easily go away after a few weeks or months and never come back, or could get worse.
Mostly the noise isn't any sign of an impending problem or breakdown.
Getting the laptop replaced will most likely get you one that doesn't squeal.
Hope that information helps a bit, I know it can drive you mad when you get a high frequency squeal, and even madder when other people can't hear as their hearing isn't as good.
The same sorts of noise are now used in areas where children hang out causing trouble, a high frequency noise is blasted out at a frequency that most adults can no longer hear but children can as it drives them insane, so if you can here the squeal and others can't that is quite normal and shows if anything you have younger hearing or are indeed younger.
Regards
Phil
Message was edited by: Philip_l