Macbook Pro loud vibration/noise

Hi!

Two days ago my macbook has started to do a loud vibration/noise like if te fan was stuck or something. The sound it's very hight and scary. I took my mac to a service center and after a couple of hours they check it and told me there was nothing wrong with my macbook. But today after using it for an hour the noise and vibration came back. I wasn't playing any games or watching videos just normal web surfing as I always do. I know that the noise and vibration aren't normal cause I've had my mac for two years and It's the first time this happens to me. Any ideas of what can be?