Q: What does the beeping sound on a Macbook Pro signify?

Very rarely, I get a single beep sound AFTER my Macbook Pro is turned on (normally, without any hitch). Does this signify any sort of hardware damage?

Also, I tried doing the AHT (online). Unfortunately my PPoE connection was off and so it couldn't connect to the internet to perform the AHT. Hence, I had to do a force shutdown to go to the grey screen to enter my password and start the computer (as there was no other way to restart to the normal/usual screen from there). Will the force shutdown (the first one I've done) harm my Macbook Pro?

The beeping made me conduct a "Verify Disk", the result of which was OK.

Please Help!