Using dictation to transcribe audio files in batch?
You can use SFSpeechRecognizer (mirror) (requires macOS 10.15+): this is made for speech recognition and it's an SDK so you can write some code for batch processing.


  Perform speech recognition on live or prerecorded audio, receive transcriptions, alternative interpretations, and confidence levels of the results.


Note that 
from https://developer.apple.com/videos/play/wwdc2019/256/ (mirror):