Thank you very much for your feedback. You dont have to regret that your monitor is dead silent. It just motivates me to try to get it replaced.
I dont have to be close with my ears to hear it. In a silent room it is audible even when I am 2 meters away from the monitor, so it is not that I am just sensitive to "a little bit of" noise.
BTW: I only work at 80 cd/mm2 (where it is dead silent), but this does not mean that I should accept a defective monitor that produces noise at higher levels.
I will contact NEC and hope that they replace it.
I also found another bug (defect?) with my monitor: When I am in sRGB mode and I change the brightness "too often" then from time to time the color temperature changes abruptly, e.g. from "cold" to "very warm/reddish". It did not happen (yet), if I deactivate the internal sensor.
One year ago I bought a 43" TV and it has perfect uniformity, makes no noise, has no backlight bleeding, no quality issues etc. and it cost ony ~300 Euros. And also the TVs from my family and friends dont have any noticeable problems.
Why do I have to go through all this pain with desktop monitors? Something is definitly wrong here... First Eizo and and now NEC. Can I not expect basic quality if I pay more than 1000 euros? This really annoys me as hell ...