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s.sarpas

Member

Registered: 2015-07-17

Posts: 5

Changing backlight brightness makes weird noise

My laptop makes a weird noise whenever I try to decrease its backlight brightness. I'm not sure what causes this noise, any idea?

I am decreasing the brightness using xbacklight and here is my 20-nvidia.conf:

Section "Device"
        Identifier "Default nvidia Device"
        Driver "nvidia"
        Option "NoLogo" "True"
        Option "RegistryDwords"  "EnableBrightnessControl=1"
EndSection

thv

Member

From: Germany

Registered: 2015-08-15

Posts: 3

Re: Changing backlight brightness makes weird noise

Hello s.sarpas,

typically laptops have two capabilities to control the brightness.

Look in /sys/class/backlight
There should be two folders with a file named brightness in it.

Try to change the values in the brightness files to find out which one causes the weird noise.
Please regard the maximum values given in the file max_brightness.

You can change the values like this:

root# echo 15 >/sys/class/backlight/???/brightness

Replace the ??? with one of the foldernames.

Be careful with small values! 0 makes the screen completely dark.

Greetings from Germany
thv

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 19,804

Re: Changing backlight brightness makes weird noise

When you say "Weird sounds" I immediately think of https://en.wikipedia.org/wiki/Microphonics.  That article focuses on picking up electrical noise from audio signals.  But, electrical signals can also cause things like multilayer surface mount ceramic capacitors and inductors  to "sing" http://product.tdk.com/capacitor/mlcc/e … effect.pdf.   

I'm guessing you are hearing something in the 8kHz range,  if you are under 40 years old, you may be hearing something in the 10 to 15kHz range.   For fun, you might install a spectrum analyzer program on your smart phone in order to get a good visual.

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