Q: Why does my ibookg4 chirp every 30 seconds? 5 chirps,then 5 chirps, then 5 more

Some users noted chirping sounds ahead of a hard disk drive failure;

that may be something to work on, backing up to an external archive.

https://www.google.com/?gws_rd=ssl#q=Mac+OS+X+iBook+G4+chirp+noises

If you have been letting the computer sleep, but not shut down or restart

recently, there may be a chance the machine may have several open

applications that could be using Virtual Memory (hard drive free space)

and that could be over-taxing the computer's resources.

Even if the report from an Apple Hardware Test should suggest the HDD is

OK, that may only mean it passed a trivial simple test, it still can fail in an

almost unpredictable way; you could lose data and your files saved in it.

So backup. If needs be, you could get files from the iBook via Target Disk

Mode, with FireWire cable, from another FW equipped Mac. If you use a

clone utility, such as CarbonCopyCloner, or SuperDuper, that could be

used (perhaps, if not too late) to attempt to make a boot/copy of iBook HDD

on another externally enclosed self-powered (AC adapter) hard disk drive.

Did you see if the computer would start in SafeBoot Mode, & not chirp/beep?

PS: another reported cause of a chirp sound, may be related to cooling Fan.

Good luck & happy computing!