I think Deep Blue's answer is spot on - if you're speaking and it is not clear, too noisy, then you call that distortion.
If you're not speaking and you hear noise, you call it "static" (if it is constant), or "crackle" (if it is intermittent). If you're not sure, just say "there is noise".
A couple of extra notes:
- "cacophony" is a rather formal word which means noise. I can tell you looked in a dictionary. ;-) It literally means "bad-sound" and refers to bad music or unorganised sounds (eg. busy traffic).
- beware of using too many adjectives! "Intermittent noisy sound" is unnecessary. Just use "noise". Same for "noisy cacophony" - we already know cacophony is noisy. Start with the noun - if it makes sense, then no need for an adjective.