WordNet (r) 3.0 (2006):

stridency
    n 1: having the timbre of a loud high-pitched sound [syn:
         shrillness, stridence, stridency]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "stridency":
   acerbity, acidity, acridity, acrimony, acuteness, arguteness,
   astringency, bite, bitterness, causticity, creakiness, edge,
   fierceness, grip, harshness, highness, keenness, mordacity,
   mordancy, pipingness, poignancy, point, reediness, rigor,
   roughness, screechiness, severity, sharpness, shrillness, sting,
   stridence, stridor, stridulousness, stringency, tartness, teeth,
   trenchancy, vehemence, violence, virulence