My 8-core Xeon Mac Pro, running Snow Leopard, has an 'odd' behavior. Every time it boots, I hear the initial successful boot tone, followed by a delayed series of 4 quieter, abbreviated but similar boot tones. The machine boots normally and operates normally that I can tell.
Mac Pro, Mac OS X (10.6.8), 12GB DRAM, 4x1TB drives.
The following apple doc refers to multiple boot beeps
Power On Self-Test Beep Definition - Part 2
But what is confusing is your description about when the beeps occur, i.e, after the normal boot chime. So that doc may be unrelated.
Try disconnecting all your periphials and see if the problem continues.
Try smc reset too.
See if it occurs if you boot in safe mode.
http://reviews.cnet.com/8301-13727_7-57383970-263/how-to-address-a-constant-rebo ot-loop-in-os-x/
Not your issue but goes into what can happen during boot process and follows with troubleshooting steps.
Why does my intel Mac Pro boot with multiple 'good' boot tones?
