Yes, this is just output. And Bach-y-Rita showed Input is digital.
What’s left is all the logic between input and output.
What’s left is all the logic between input and output.
We gain a pathway for investigation backwards. What neural substrate is active in generating the speech data? Work backwards from there.
We already have a useful pathway for investigation: data from speech/sign of a speaker of a particular language. In fact this already yields a kind of overabundance of data. The tricky part is finding the right kind of data via careful experimentation and organising it, by building explanatory theories of language that meet the conditions of evolvability and learnability.
(Which is not to say that cognitive sciences can't shed any light on this, but studying the brain independently of linguistic experimentation is a dead end IMO. Brain imaging studies coupled with linguistic studies have yielded interesting results - see Andrea Moro's work on "impossible languages").