public address system vs verbalizer

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. 

verbalizer

noun
  • A thing that or person who verbalizes; frequently contrasted with visualizer. 

  • A morpheme, particle, etc. that converts a word into a verb. 

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