In early January I bought U2515H. I was quite happy with it until I noticed electric squeak from the monitor. I was quite surprised with it because I've never experienced such an issue with any monitor in the past. At first, I thought that it could be problem with frequency so I've unplugged video cable and launched monitor test (buttons 1 and 4). I went through different colors and once white color appeared on monitor, it started to make quite audible high pitch noise. I tried different power sockets, plug power cord to surge protector with electric noise absorption but nothing changed. By the way, for example I have different speakers and none of them have such an issue (you may know that speakers are sensitive to electrical noise). I also brought monitor to one of my friends who leaves in a new house with brand new electric wiring but same issue occurred. So I've contacted with Dell support team, we tried several solutions but nothing helped. So I was advised to make a replacement. Since I'm giving only one chance in such a situations so I requested for the RMA and it was done through local Dell service partner. By the way service partner engineer confirmed me that such an issue can be related only to fualty monitor PSU and to nothing else. I spent several days to find for a worthy replacement for U2515H but didn't find anything better regarding my requirements. Thought about the U2518D but unfortunately it doesn't have flicker-free feature which is very important for me due to sensitive eyes. So I went to the store and bought again U2515H. I trusted the words of Dell support center specialist that issue with previous one monitor was just unfortunate misunderstanding but I faced again with the same issue! The higher the brightness - the higher the noise from the monitor! Is this the highest quality standard that your support center specialist spoke about? I'm very disappointed with that issue. So what is my next steps? Make replacements until you provide me with correctly working unit? By the way on one forum I found a thread from the person who faced with such an issue on other model and it took 3 times to make a replacement so he was provided with a correctly working device. Looks like I will have to go through the same quest.
Per the Manual page 35, the U2515H Brightness and Contrast should be set to the Factory Defaults of 50/50.
Then, any further Brightness or Contrast changes should be done inside the GPU video card control panel. As an example, see below the Nvidia Control panel for Brightness =