I'm using an APC BR1500 as a battery backup unit. Whenever I disconnect it from the AC source and it switches to battery mode, my monitor makes a loud buzzing sound, which is similar to the sound coming from the UPS, but louder. I'm assuming this is because when on battery mode, it does not output a pure sine wave, but a "stepped sine wave". The noise doesn't really bother me, since it only happens on a power outage, but I am worried that this could damage my monitor. I am using an SGI GDM-5411 monitor, which i'm told is the same electronically as a Sony GDM-F500R, which is more common. Should I be worried about this buzzing noise ? It doesn't affect the image at all. The image is still crisp, clear, and bright, with no distortions while using the battery.