Unexplained background sounds and voices in recording

Can someone listen to a few voice text messages and give opinions on how could Garbled voices appear to be heard when the person speaking pauses or at the beginning or end of the voice text message

EVP … https://en.wikipedia.org/wiki/Electronic_voice_phenomenon

There are examples on Freesound … https://freesound.org/search/?q=EVP

So in your opinion it was fabricated to sound like that? Or could it have been purposely added to the recording to make it appear as there was another persons voice?

In my opinion it’s just noise, not a second voice .
That it occasionally sounds like whispering words is audio pareidolia,
aka Rorschach audio, (analogous to the inkblots).
Digital audio data compression makes EVP more likely than with Ye olde analog audio.