M1 iMac buzzing / whining noise with low display brightness

My first M1 iMac as well as my exchange unit are causing a high buzzing / whining noise. In the first place I thought it comes from a misaligned fan. After a tip from another user I found out, this comes from the display itself. If the brightness is between 80-100% the sound is gone - if the brightness goes below this (e.g. in the evening) the noise is coming back.

Try something out, put your Backlight at full brightness, sound should be gone? And when you put backlight lower step by step the sound should come back.

It looks like that all of the new M1 iMacs are affected.

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