My laptop fan is very noisy?

What can be the reason for this, what can I do about it?

The fan or your entire laptop may be dusty on the inside, which is why the desired cooling effect only occurs at a higher speed and it is very loud as a result.

Nothing that needs air when it gets too hot. If you have more air under the laptop it will be cooler and the fan doesn't have to work as hard so maybe a pad with holes in it so that cool air can get through. It is very bad to have a laptop on soft things like mattresses then it gets very hot.

Clean the fan, clean everything, install the fan driver / fanspeed and see how warm it is and if it is cold then you can turn it less. Renew thermal paste on the coupon fan under the laptop so that the inner fan has to work less, e.g. Place CD cases under so that there's more air from below