Modern day Macs no longer issue the dreaded "Chimes of Doom" when they fail to pass their hardware startup tests. Instead, they beep. But, they'll beep differently depending on the problem encountered and the Mac model. Here are the codes:

On an iMac, Blue and White G3, Power Mac G4 (PCI Graphics), and PowerBook G3 Series (Bronze keyboard):

1 beep = No RAM installed/detected.
2 beeps = Incompatible RAM type installed.
3 beeps = No RAM banks passed memory testing.
4 beeps = Bad checksum for the remainder of the boot ROM.
5 beeps = Bad checksum for the ROM boot block.

On a Power Mac G4 (AGP graphics):

1 beep = no RAM installed.
2 beeps = incompatible RAM types.
3 beeps = no good banks.
4 beeps = no good boot images in the boot ROM (and/or bad sys config block).
5 beeps = processor is not usable.

Should you hear any of these beeps, and haven't just installed new RAM or otherwise mucked about with the insides of your Mac, Apple suggests that you call your Apple Authorized Service Provider for troubleshooting assistance.