Faulty fan is the most likely.
Faulty hard disk is possible but much less likely.
Overheat trip from a faulty sensor.. which causes the fan to scream at high speed.. over 5000rpm.. whereas it normally runs at 1500 and can be barely heard. This will give an error overheat message if it happens.
Record a video on your phone of the noise.. then simply get it replaced.. you are well inside warranty period anywhere in the world. The build quality on the TC is less than spectacular. So you might decide the replacement (usually a refurbish) should be disposed of ASAP.
Copy anything you need or want to keep on the TC to another drive.. right now.. because it could be pointing to a major breakdown.