If they are speaking loud enough, you wake up and the episode ends.
The veil between the sleep and awake state is very thin, even though they are located in 2 separate dimensions and consist of completely different actions. Whilst you are experiencing sleep paralysis, you may be unable to move, yet something from the awake state can jolt you out of the sleep state and the paralysis.
You may not recall the words which were spoken to you during the episode. The sound itself is what causes you to wake up.
It’s a bit like being woken up from a deep sleep. Someone has to raise their voice to rouse you.
When you awaken, you are perfectly fine physically, apart from the distress caused by the memory of the incident.
I experienced sleep paralysis chronically for over 30 years. You’re more than welcome to read about my personal story as well as blogs and books that I have written about sleep paralysis.