Hint: You will get personal data protection problems if you record voice in hidden manner and without explicit consent of the person. See https://docs.getodk.org/form-question-types/#planning-for-background-audio-recording.
I want the sound recording to start when the form is started and the user cannot disable it. Currently, the user can disable the sound recording. How can I prevent the sound recording from being disabled?
There is no way to do that and tracking background location works in the same way. Users should be able to disable those options if they don't feel secure enough to share such data.
What I've seen some projects do is to make payment contingent on whether or not background recording was on. And if it was off, then a supervisor can have a conversation with an enumerator about why it was turned off.