shrillness vs stridency

shrillness and stridency both are nouns.

Word	Noun	Adjective	Verb	Adverb
shrillness	Yes	No	No	No
stridency	Yes	No	No	No

As nouns, shrillness and stridency are synonyms defined as:

shrillness and stridency: having the timbre of a loud high-pitched sound

Other synonyms of shrillness include stridence.

shrillness (noun)	stridency (noun)
having the timbre of a loud high-pitched sound	having the timbre of a loud high-pitched sound
the quality of being sharp or harsh to the senses