I agree that this may be possible. But after reading the article there are several things that don't pass the sniff test. Hopefully this will get the peer review it needs.
My first thought was the website for this story was infected with a browser virus, and the incredible story was there as candy to draw us in.
Infecting multiple OS, using some common hidden/unknown USB feature seems difficult to believe. What is the commonality in chipsets? The virus would have to run at the BIOS level.. right? Under the OS? Injecting itself up into OS' that it supports? Sure, there are few motherboards. and I've also heard of viruses that live in RAM/GPU and survive reboots. I'll also forgive people for possible misusing "ultrasonic" when they might mean - higher/lower frequencies than humans can hear but the PC can generate. Also don't forget - video cards and other electronics make noises too - I had a video card that when drawing at high FPS made a very high pitch sound that could be manipulated (I'm one of those weirdos who can "hear" CRTs). Maybe the fan is sending Morse-code.
This is also an interesting network driver. I assume he was doing packet sniffing from within the OS. I can see the following - the OS sends data packets to the network card (which go nowhere because the cable is pulled out) - but the infected BIOS sees those and copies them out the speaker. However, he pulled the network card... so I would expect the OS to shutdown all connectivity features - so what was the sniffer attaching to? (or rather - what was he sniffing? - no pun) Either that or a software driver had to be installed (or hook the virtual loopback). All possible. Although on my laptop only the wifi/bluetooth can come out - the Ethernet is on the mainboard.
All of it may be hypothetically possible. I can't wait for an update and see the results. Need to think simple - those kinds of attacks tend to work.