Very weird noise coming from thinkpad 390E

[CapCor]

At first I thought it was the hard drive. Then I put headphones on. I recorded this using the line in on my desktop. http://vocaroo.com/i/s1s0H81chNtL. If I mute the OS you cant still hear it. If I mute it using the hard ware volume knob you cannot hear it. I have tried Windows 2000 and POSReady 2009 and they both result in the same problem.

[automobus]

I suspect noise is coming from infrared circuitry. What happens if you disable infrared?

I hope a few longtime 390E owners will contribute their observations. Did a new 390E, back then, make such sounds? Do 390E make such sounds today? It might be a problem caused by age, for instance: deteriorated/bad capacitors.

[Norway Pad]

It does indeed remind me about the EMI noise some kind of transmitter or badly shielded / defective circuitry makes. So Automobus' suggestion can be worth trying. Infrared light does of course not interfere, but the circuitry generating the signal might do. Probably a total shot in the dark, but do also try to remove your PCI modem card. My feeling is however that you're looking into a permanent defect on your motherboard, presumably the sound chip.

My 390X, which has the same ES1946 audio controller as your 390E, is totally quiet when I don't play anything. It has a Win 2000 / Linux Antix dual boot, and in Win2000 the sound works as it should, while it doesn't work in Linux. But despite the incompatible driver in Linux it doesn't give out any static sound like we hear on your sound clip.