What sound does bearing make when it needs to be lubed?

I don’t know what it sounds when bearing needs to be lubed.

Bearings never need to be lubed, but if it’s making some fairly decent noise you can give it a drop to make it quieter and smoother.

It’s usually a loud gritty sound. I recommend cleaning it in acetone/lighter fluid/paint thinner and adding a drop or 2 of thin lube/thick lube depending on what you have and what type of play style you’re trying to get out of your YoYo.