I got my Lenovo Z580 laptop last month.
I haven't noticed any sound before, but today i noticed something strange sound coming from left bottom corner.
It is some think that i can;t distinguish, something like chik chik.. ..
The Z580 only has one single fan, and I honestly think it's the fan.
Try using Lenovo's utility to clean the fan, there should be a dedusting option, use that.
If not, you can always open up the thing, and add some lub to the fan.
Had a similar problem with a Client's S100 once, opened it, lub it and walla.