MBP (older model) making funny noises near fan duct

[potlatch]

My MBP is making funny noises when I turn it on. It's been happening a month or two now.

I've assumed it's dust in a fan which gets dislodged after time. As it becomes more regular, it seems vaguely connected with temperature. After the MBP has been on a while, the noise goes.

This evening, I noticed that it's directly related to the brightness of the screen; if the screen is off or very low, the sound is less bad; towards middle-brightness, the noise is worse; and at full brightness it's completely absent.

Does anyone know what's causing this? Should I worry about it, or is there anything I can do?

 

[tobyg]

Sounds like it might be the inverter in the display.

Still have some applecare left? If so, take it in.

 

[DjStiky]

I have the same problem with my 15" Macbook Pro

Got an appointment with a Genius at the store, they ordered me a new screen.

 

[potlatch]

I'm well past the warranty and no Applecare. The machine's a few years old.

Is there anything else it could be? Dust/fluff, or anything that doesn't require an unemployed person shelling out loads of cash for something to be fixed.

How much does this screen replacement cost anyway?