I’m speaking from personal experience. In 1982, when the comic was published, tape recorders were not considered a novelty, and had been in common usage for many years. The humor in the panel derives from the stereotype of a nerd and how the stereotypical nerd is supposed to sound.
Take a look at the copyright date on the comic. This was right at the time when tape recording, not just playback, devices were becoming common.
I’m speaking from personal experience. In 1982, when the comic was published, tape recorders were not considered a novelty, and had been in common usage for many years. The humor in the panel derives from the stereotype of a nerd and how the stereotypical nerd is supposed to sound.