Possibly Harddrive failure or maybe the psu fan or heatsink bearings have gone.
Backup/backup everything thats important.
Then open the case and remove any dust/residue.Then see if you can pinpoint the noise.
OnePlus 5T review: Hands-on
Illustrator Andrés Lozano on his improv line work, brazen use of colours & hand sketching
iPhone X review
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