My best guess its an unfunny "Easter Egg" that triggers after something like 5,000 hours of uptime. I think I remember some bug in Boeing or some other system that they need to actually be rebooted every 100 days.
I'm one of those people who thinks easter eggs are great, and miss the days when you had a decent chance of coming across one in a program or game.
The FAA does not agree with that. The FAA probably thinks that easter eggs in avionics software are a crime. And I agree with that position! Aviation, medical, military, and any other critical software should not contain easter eggs, and it should be an offense to knowingly include one. Stuff like this (even though it's probably not an easter egg) is a great example why. Just imagine the cost to patch this if it's widespread... and it has to be patched, because this one can literally kill people if you don't fix it (think spooked flight crews making rushed or generally poor decisions if you don't think this is potentially lethal).
According to the researcher who found it, "they didn’t think it was very funny.”
I love easter eggs myself—classic Apple software in particular had a lot of these, and I really miss finding them—but they're admittedly a risk. I remember one obscure Easter egg in Mac OS 7.6 that occasionally caused crashes at boot time after displaying a bizarre message about how "bluets and granola bars / make a chewy snack". Cute, but probably not something Apple wants to be getting customer support requests about.
As far as the topic at hand, I don't believe these weird noises are an Easter egg, either. I'd guess it's a recording patched in somehow by someone who works for the airline.
Personally I draw the line somewhere around "software that's controlling something". If software can directly screw up or cause damage in the Real World™, that's a good reason it shouldn't have easter eggs in it. If the trouble has to indirect through one or more meatbags who know better before becoming reified, well, the harm caused by any easter eggs is probably much less than the harm caused by reported bugs already closed WONTFIX with a laugh. (Note: PAX do not in fact know better, ever, as any airline employee can and will tell you.)
I looked up the story behind the "Bluets and Granola Bars" easter egg. Apparently, the System Error Handler, part of the boot ROM, used to display a popup that said "Welcome to Macintosh" at startup, before the operating system loaded. However, in System 7.6, this was replaced by a new splash screen with the Mac OS logo, and the old "Welcome to Macintosh" message in the system resource file was replaced with the Granola message (probably under the assumption that it would never be shown). However, if the operating system fails to suppress the boot ROM's popup for whatever reason, the Granola message shows through.
I read in Slash’s autobiography that when he got his pacemaker installed they set it at a certain heart rate, but when he played his first live show, he felt a handful of thumps in his chest and thought it was bigger pyro than normal.
Turns out his pacemaker was shocking him because it thought his elevated heart rate was a danger! They fixed the setting.
Why do you think is it a bad idea to have a defibrillator that flashes PSYCH on screen when the Shock button is pressed, but then delivers an actual shock a second or two later? It would happen only on the fifth cycle of CPR or so!
