Laptop screen buzz/hiss and flickering?

Hi, recently my laptop screen has started to buzz/hiss and occasionaly flickers with the flickering getting worse the longer i leave the laptop screen on. The flickering starts to go down if i turn down the brightness of the laptop but the buzz remains. I read that this maybe caused by a dieing laptop screen inverter but I am not sure if this is the cause as I heard that it is due to the AC adapter power needing to be converted but with my laptop, if I unplug it from the AC adapter and run it with battery, the problem still persists. would anyone be able to help me identify what is wrong?