tft noise?

The tft on my laptop makes a sort of quiet hissing noise, that you can only really hear when there's nothing else on.

Is this normal, do TFTs make noise? I'm guessing its the inverter or whatever the bit that does the business is called...

Any ideas? Is my backlight gonna go??

*edit* this is on my cheapo toshiba laptop; after firing my iBook up from sleep, it doesn't seem to make any noise at all.

The iBook is running off the mains, whereas the tosh is off battery.

*more edit* actually I don't know if it is the TFT after all, after switching it off, and after a short pause, the noise begins again. Hmm! Just the internals of the computer??

Thats the great thing about me mac, absolute silence!

Ok, let me put this another way- those of you with laptops, when the fan and hdd are off, stick your ear on the keyboard. Hear anything??

Its cause TFT monitors are backlit by cathodes that use inverters. You're hearing coil whine from the transformer.

Ok cool...but how come my mac is silent? Better quality transformer?

I get coil whine from my laptop, most noticably when I open new windows or do anything that changes the brightness of the screen. It usually lasts under a second but there is an ever-so-slight noise normally anyway. This is with a 1600x1200 screen, so not a cheap one :)

Aaah man, a guy at work has a dell with 16*12 screen, and its just..eyestrain! But, very handy for dev work, which is what he does.

I'll have to get me something bigger than 1024, and soon...

Thanks for the replies...btw, coil whine?

I've no problem with the screen, I just have the laptop closer than I would a normal desktop CRT or LCD. I can always whack the dpi up if necessary to make the text larger (and sharper than just dropping the resolution too).

Coil whine is created by transformers, typically under load. I think it's to do with resonance of the metal through the expansion due to the increase in temperature combined with the frequency of the current, BICBW

do not really get any noise from my ibm thinkpad only fan and hdd noises