The fan in my laptop computer speeds up and gets louder
While working on your computer you may notice the fan inside the computer will randomly speed up and slow down, often getting louder and quieter as it changes speeds. As long as the fan continues to spin and doesn't completely stop this is completely normal for computers, especially laptop computers.
To help keep the noise down in computers most manufacturers today have variable speed fans, which means that the fans within the computer are capable of changing their speed depending on how hot the computer is getting. Usually you'll notice that the fans will speed up when working on the computer or playing games. Each thing you do on your computer cause your processor, graphics card and other devices in your computer to work, which causes heat. If the speed of the fan is not taking out enough of the hot air or bring in enough cooler air the fans will need to increase their speed to help keep your computer cool and prevent any damage.
The reason you're more likely to encounter this situation with laptop computers is because of the size of the fans in them. Smaller fans don't move as much air as a bigger fan and therefore must go faster when a computer is getting hot.
Tip: With most laptop computers cooler air comes in through the bottom of the laptop and the hot air escapes from one of the sides. If you're working on the laptop from your lap, this will often constrict the airflow causing the computer to heat up more. Try working on a hard flat surface instead of your lap. Having a cooler pad or other device that gives the laptop even more room to breath beneath it can also help reduce the need for the fan to speed up.