This may be anecdotal [and sleep deprivation may impact different people differently] but it has a huge impact on me.
I used to use memrise [flash card style memorisation] to learn new words/concepts for years [25minutes, the first thing after waking up, every single day] and I know from experience how sleep, food, hangover, etc. impact my performance.
Sleep has a gigantic impact on my memory, focus and creativity — I believe it is responsible for really high variation in IQ points [10 - 20, but that's my rough guesstimate]. This is a more qualitative assessment but whey I sleep 4 hours it resembles a high level of depression — I lose motivation and all of my natural curiosity is gone [eg. usually, reading/learning brings me happiness, but it's all gone when I'm sleep deprived].
That's why I haven't used an alarm clock for years now.
Voice recognition is 'on' all the time as it needs to recognise 'keyword'. All you need then is simple transcription into text.