Speech-to-text on the Android is sometimes entertaining. The results are often unexpected. I have all the filters turned off, so sometimes random profanity even gets thrown in. Like foreign speakers of English often show me appealing creativity with my native language, speech-to-text sometimes does the same with those "dirty words."
I've never researched speech to text. I assume a sound file gets transmitted somewhere, probably to Google in the case of Android, where it gets decoded and sent back as text. Since I switched the default Android keyboard to one called TouchPal, I'm not sure if Google is still the back end, or if it's now TouchPal.
Below is this morning's example of speech-to-text turning the name "Javier" into "hobby air." It probably has something to do with my Southern accent.