Whistling noises from inside

[editestare]

Just formatted my computer and cleaned it from dust yesterday and noticed that it makes this boiling teapot whistling sound that lasts 7 seconds and repeats itself after around 80 seconds. What's the cause? Is it dangerous?

 

[Ayman IBreak]

you might have got dust in places like pci slot or ram slot
when you were cleaning did you take the ram or the GPU out ? if you did clean the slot

 

[editestare]

Didn't took anything out, I only added a DVD-WR which I took out later that day.