This is kind of random, but see if you can follow my thinking. Though I suppose if you weren’t
geeky familiar with the TV shows in question, it may not make sense to you; carry on.
Back in the 70s, when "The Six Million Dollar Man" and "The Bionic Woman" were on TV, the "bionic sound" became somewhat iconic (still is). You know, the sound effect they used when they used their bionics for running, or throwing something, or whatever. I don’t even know how to describe it—ratcheting?—other than the completely lame "na na na na na" slightly-onomatopoeic phrase, but to my mind that bionic sound is the "tech sound" of the 70s.
Similarly, I think the iconic "tech sound" of the 80s was the sound of Transformers, er, transforming. From the cartoon, of course. It was just something that worked, on an almost intuitive level; and I can’t think of many people I’ve run into who wouldn’t instantly understand what it meant to hear that sound effect.
(Both of these meanderings were jarred loose one day when I was musing on the fact that there was both a Transformers movie and a new "Bionic Woman" series this year.)
My theory here is that it seems to be decade-oriented, like everything else. So, what’s the "tech sound" for the 90s? Sound of a modem dialing and handshaking? "You’ve got mail," courtesy of AOL (ugh)? I can’t think of what else could be drawn from pop culture that had an impact like the bionic and transforming sounds.
Same thing for the 2000s—what’s the iconic sound?