NaN is a sound, emitted by mathematical equation solving programs such as MatLab or Mathematica. It causes an interesting reaction in some people, usually in math majors or physicists that are forced, by homework or some other form of institutionalized sadism, to rely upon such programs. After three nights work, getting sections of code to run individually, and two weeks of bug fixing, and before all of that a month of theory working, a researcher is understandably on edge. When finally the numbers are poured into the process from the tediously made Excel spreadsheet, the researcher goes and takes a break, gets a bite to eat, sleeps(smoke, if they are a mathematician). Anything that will get her away from that computer screen.

When the researcher finally returns, they will begin scrolling through the data, looking for it but never expecting it. If they were in the room at the time, they'd of heard it, but even if they weren't the sound reverberates through their minds:

¡¡NaN!!

At this point the researcher is crying into his notes(you'll note that this also has the effect of bit flipping the researcher's gender). Weeks of work will have been completely useless for a reason that isn't immediately apparent. The sound reverberates through their soul, even though there is a good chance they don't believe in such a thing. They will feel a deep seated urge to either join the circus or send Stephen Wolfram a pipe bomb. Everything about their research they thought they understood has fallen from focus and the world is nothing but pain.

NaN is the sound that terror makes.

In Mathematica, NaN sounds like a beep.