thrum vs hum

thrum and hum both are nouns.

Word	Noun	Adjective	Verb	Adverb
thrum	Yes	No	Yes	No
hum	Yes	No	Yes	No

As verbs, thrum and hum are synonyms defined as:

thrum (noun)	hum (noun)
a thrumming sound	a humming noise
	the state of being or appearing to be actively engaged in an activity

thrum (verb)	hum (verb)
make a rhythmic sound	sing with closed lips
sound with a monotonous hum	make a low continuous sound
sound the strings of (a stringed instrument)	sound with a monotonous hum
	be noisy with activity