what do you call a part of a song where there’s no music and just random audio

Bridge?

"fill"

DeKay

Brap

Cut and paste "music"  by "producer/DJ" types don't necessarily  follow typical song structure. You might call it a "break"

I'd say a bridge.

An interlude

So many of the songs on Madvillany like Bistro or like the outro on Americas Most Blunted are just random clips of conversations. Is there a name for these part of songs (like chorus, verses, etc)

I got this,..

In the 70’s, we used to call that part of the song the “dump”. Not exactly sure why, but that’s what we did. Listen to “Forget Me Nots” by Patrice Rushin. In the middle it just breaks down(breakdown was another term) into a bass and drum riff that had nothing to do with the rest of the tune. Perhaps to just give some more beats to dance to. I don’t know why, but it was just accepted as what you would do as part of the song.