alt Hacker NewsWith proper volume control, even one bit could probably sound voice-like enough to a person in the 1980s.
It may be feasible to retrieve a pcm for a very short clip by playing the same recording at different levels which then could be converted on the same machine to a sequence of opcodes playing a more realistic voice.
On the Speccy at the time we had no volume control, only frequency... or more accurately you could but the frequency and the volume were tied somehow: https://retrocomputing.stackexchange.com/questions/14655