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You ask a good question, and I'm not sure I can answer it for you, but here are some observations about your example.
1. It reads like a screenplay rather than a narrative story. If that is your intent, then it's fine as it is.
2. You've brought the radio from the background to the foreground. If it's background noise, the character will be barely aware of it.
3. You could state in the narrative preceding the monologue that the radio has poor reception and that this station is frequently interrupted by static (and indeed overlain by it, giving the announcer a tinny voice). Then, instead of writing '[STATIC NOISE]', you need only write a single ellipses (...) wherever you need static to break the monologue.