Various office sounds
"Workplaces are quieter now. No longer do you suffer the scream of dot matrix printers or tweedling of fax modems, let alone digital squeaks."
I sit next to our multifunction printer, and occasionally hear it (very quietly) receive a fax. And our office actually has a dot matrix printer, for filling out one particular form in carbonless triplicate. A nostalgia-inducing noise - when heard from 50 feet away.
At my first office job, everybody's computer had Outlook (I think, it's been almost 20 years) set to its default 1-bing "incoming email" tone. I couldn't tell when it was mine or anybody else's, but a few moments in Sound Recorder and mine binged 5 times instead. Now, years later, I did something similar with our instant-messaging app.
One time, when a co-worker left his computer unlocked, I quietly switched his incoming email sound to a sheep bleating. LOUDLY. He laughed so hard he decided to keep it. Six months later, he was giving a presentation to about 40 people. Some of the ones in the back were nodding off a bit. Then he received an email (*not from me!*). As he was hooked up to the projector at the time, his computer helpfully routed the sound to the ceiling loudspeakers. 100dB of bleating sheep will wake almost anybody...