megaphone vs sound system

megaphone

noun
  • A portable, usually hand-held, funnel-shaped device that is used to amplify a person’s natural voice toward a targeted direction. 

  • Mouthpiece or promoter; one who speaks for or publicizes on behalf of another. 

  • A cytotoxic neolignan obtained from the laurel Aniba megaphylla. 

verb
  • To use a megaphone; to speak through a megaphone. 

sound system

noun
  • An electronic system used to reproduce sound. 

  • A mobile platform playing selected recorded music, set up as a social event, often with an entrance fee. 

  • The set of speech sounds that make up a language; a phonology. 

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