PowerBook G4 ...beeps!!

3+yo PowerBook G4, 1.5GHz PowerPC G4
I am using this as a backup while MBPro is 'in the shop".... in the last week, with no apparent reason/cause, there is a random and loud BEEP sound. I never experienced the sound before....and wonder what it is. Everything about the unit works fine.
Ideas? thanks.

Low battery warning?

no. battery is 99%....thanks for suggstion.
I have since read that there are various BEEPs for RAM memory issues, but they also don't apply. since my computer is being shipped to Depot, second time in 8 days, I have this one as a backup....just would like it not to crash on me.

Well you are noit alone. Have a look at this link and suggested fix:-

http://forums.macrumors.com/showthread.php?t=119183

My powerbook G4 has done it periodically over the last year. I've never found a solution. All I know is that it's a hardware level "beep," happening even when the system is muted.

unlike the macrumors posting, my beep happens when I'm on battery with nothing attached.

It was doing it a lot shortly before my first hard drive failed. Still does it periodically with a new hard drive (different brand).

My beeps have no sequence to them.

Scott