The "gui-gui" thing is something called "gitaigo" in Japanese. The Japanese language has TONS of words for things that are basically sound effect words. English has them too, but I've a suspicion that we have less. Words like "bam" "pop" or the like are what we're talking about here. There's a great guide at
this site.
I'm glad you cleared up what level of security you're talking about (military), because at first, I was thinking "Wal-Mart? Classified? Give me a break..." :P