I have a Panasonic LCD BT-LH17000W monitor but I noticed a hi-frequency noise from the back of the unit - kind of like an "electrical hiss". I was just wondering if this was normal for a LCD, since it reminds me of the kind of noise a CRT makes !
Anybody works with that monitor ?

Probably it's inverter making that noise. It generates high voltage for screen. There is small transformer inside inverter. That could make a noise. In my eyes it is a warranty case. Inverter should be replaced.

Might be a high frequency noise almost out of your hearing range. CRT tubes warming up on old black and white Philips TV sets used to almost send me insane when I was a kid. ( On reflection, maybe they did. ). If you have children, ask them. They may well hear a clean extremely high pitched whistle.

It may be a fault but it might also be a normal operating state.

There were a problem with the monitor. I had it changed.