6. The busy signal ballad
Between call-waiting and speech-based signals ("The number you are trying to reach is busy..."), the soothing sound of a busy phone is something you rarely hear these days. Unless it's sampled in a future Puff Daddy song, odds are, it'll be just another random tone to tomorrow's teens.
7. The dot matrix jam
Today's printers might actually work -- well, most of the time -- but boy, do they lack the vocal prowess of their predecessors. The bone-crunching sound of the dot matrix is one of the most immediately recognizable noises in yesterday's technology. What other sound, after all, so deafeningly conveys the message: "Hey, buddy: Get ready to fix a paper jam"?
8. The slide projector shuffle
It may very well be the quintessential sound of boredom: the unforgettable click-clack of a slide projector shuffling through its slides as someone shows you a bunch of images you have no interest in seeing.
Ah, the memories...