Sine-Wave Speech Demonstration https://youtu.be/EWzt1bI8AZ0?t=74
> Sine-wave speech is an intelligible synthetic acoustic signal composed of three or four time-varying sinusoids. Together, these few sinusoids replicate the estimated frequency and amplitude pattern of the resonance peaks of a natural utterance (Remez et al., 1981). The intelligibility of sine-wave speech, stripped of the acoustic constituents of natural speech, cannot depend on simple recognition of familiar momentary acoustic correlates of phonemes. In consequence, proof of the intelligibility of such signals refutes many descriptions of speech perception that feature canonical acoustic cues to phonemes. The perception of the linguistic properties of sine-wave speech is said to depend instead on sensitivity to acoustic modulation independent of the elements composing the signal and their specific auditory effects.
Then the player uses both as inputs to ai (some hand waving), which now has enough to put the pieces together and produce something intelligible again, in the speaker's voice.
They make voice-like synth sounds, different for each character, that are about the length of the text they're saying. It adds prosody and intonation to the text-based dialogue of the game.
Edit: oh sweet there's intonation too. Were these all made manually?
By pairing the audio with the text, you would almost certainly convince the listener that they can understand it.
Edit: typo