Hi. I'm Brian and I will do my best to help you.
Most computers, when you start them, run what's called a "power on self test" or POST. If a hardware problem is detected, they give a set of diagnostic beeps in a code pattern. Your computer manufacturer's web site should have a manual for your exact model of computer that explains what the beep codes of the POST mean.
If it's not a beep code, it could be some other hardware failure making noise, such as the fan that you mention.