svukelich, thanks a lot for the suggestions. I have tried most of this already.
1. Have tried zero USB devices connected, including internal headers, except a basic mouse and keyboard to login. As soon as iCUE starts the disconnect sound occurs. I've tried many drivers and versions of Windows including older versions of 10.
2. This one doesn't change anything since it happens with zero USB devices, it's when the iCUE software loads even if there's zero Corsair, or any other devices attached.
3. The devices work fine on 2 other test systems (Commander Pro, K95 Platinum RGB) so they should be okay. I have also tried many versions of iCUE and fresh 10 and 11 installs, and it does it regardless of if those devices are connected or not. It is just when the iCUE software loads on my X299 system. If there's no iCUE, there's no sound, as soon as I load it, it happens.
4. I think the disks are fine, I have tried 2 NVMe drives and 2 different 2.5" SATA SSDs with both Windows 10 and 11 during my testing.
5. I could try that, thanks, I think the memory is good but who knows. Motherboard is also a potential one I guess though I've not had any issues with it beyond this issue so I would be surprised.