You need the user to download ‘enhanced’ or ‘premium’ voices in the settings app. (Settings -> Accessibility-> Spoken Content -> Voices -> [Language of choice] -> [Voice of choice] -> Enhanced or Premium)
In the app you have to search for the enhanced or premium voices when doing TTS.
Heres an Objective C example, I’m sure there’s an easier way to write it in Swift. https://github.com/osmandapp/OsmAnd-iOS/pull/1156/commits/0b...
I’m not sure if you’ll find this acceptable from a UX point of view but there’s an option to play with if you’d like.
The rotor is pretty much unable to be cooled too.
https://carbuzz.com/news/mazdas-new-rotary-engine-variable-v...