narrator vs public address system

narrator

noun
  • The person or the "voice" whose viewpoint is used in telling a story. 

  • One who narrates or tells stories. 

  • The person providing the voice-over in a documentary. 

public address system

noun
  • An electronic voice-amplification apparatus, usually containing a set of two loudspeakers and a central control unit, used for singing, giving a speech, play-by-play commentary at events, or broadcasting in public areas like in airports or stations. 

How often have the words narrator and public address system occurred in a corpus of books? (source: Google Ngram Viewer )