Most BIOSs have a system whereby if anything goes wrong in POST (Power On Self Test (basically just tests that the vital hardware is functional)) it will beep a few times. Most are 1 - 8 beeps long, but some BIOSs have stupidly long codes. Anyway, it will beep in some way if some piece of hardware isn't functional as expected, and by checking the BIOS documentation you can get a reasonable idea what the problem is.

I've never had to deal with a beep code that wasn't simply a piece of hardware like a GPU or a stick of RAM being bumped out of its housing.