sibilant vs vociferous

sibilant

adj
  • Characterized by a hissing or hushing sound such as the s or sh in sack or shack. 

noun
  • A consonant having a hissing or hushing sound such as the s or sh in sack or shack. 

vociferous

adj
  • Making or characterized by a noisy outcry; clamorous. 

  • Vocally and forcefully opinionated. 

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