I keep turning visual notifications for sound to none in Ease of access > Other Options but it keeps on blinking all 3 screens with every ding or dong. Beside it being very annoying that turns any video running to black and some programs can't resume video after that. Even that wouldn't be overly annoying if it was for my security cameras always opened on one of the monitors and I have too restart damn program every time otherwise on the program I can only monitor 2 black cats fighting in the tunnel at night.
Changing options to blink only default screen or just active title bar does not change anything. I made that problem a bit less often by turning User Account Control Setting to Never notify but that doesn't solve problem with other notifications.
Wander if there's a registry setting for that.