A few questions I have:
- Does the sound happen in OS 9 as well?
- Does the sound play only while other sounds are playing?
- Does the sound play while a CD is being played (from a drive that supports digital audio transfer)?
- Does the sound happen only while the hard disk or CD-ROM is being accessed?
This is very weird indeed. My only hunch based upon the above questions is that something else in the system is sharing the sound chip's DMA channel, which might cause these squeaking noises you describe. I once had a PC with a sound card that had bad Linux drivers and the sound card would emit chirps whenever I accessed an IDE hard drive because the drive shared a DMA channel with the sound card. The thing is, though, this sound card was an ISA card, and the chip inside the iBook is on the PCI bus. And I'm under the impression that DMA conflicts are rare on PCI. (And I don't know Mac hardware very well, maybe Macs don't even use DMA in the same way... oh well, this post may have been totally useless. Sorry.) 🙂
Alex