I remember well into the 2000s having it be usual that, while wearing headphones directly connected to the computer's onboard audio, with quiet or no music playing, I could hear characteristic electronic noise for various operations. In particular when printing, before any physical noise from the printer, I could hear long bursts of quiet bleeps and bloops.

I get a little of that with fans these days; I have a processor intensive cron job that I am reminded of when the fan across the room ticks up in speed.