Radio Shack used to sell the SPO256 text to speech chip. I had a bunch of them and the speech was barely understandable. It was worse than Talking Sam on the C-64.
There’s a recording of what the SPO256 sounded like on its Wikipedia page:
In the same video, there's a fun moment where they demonstrate constructing a simple spell checker out of unix primitives, and the demonstrator comments that "unix" is a word unlikely to ever appear in the dictionary: https://youtu.be/XvDZLjaCJuw?t=551
Of course, now it's in every dictionary!
Yes, it is certainly difficult to understand the sound. However, all these years later, the same could be said of remote video connections in which speech is sometimes replaced with undecipherable squeaks and echos.
I'm surprised that zoom et al. have not developed a scheme to show text during these squeaking times. After all, any meeting has people and computers that could detect a temporary problem, mandating a temporary switch to a dictation mode.