louden vs alter

louden and alter both are verbs.

Word	Noun	Adjective	Verb	Adverb
louden	No	No	Yes	No
alter	No	No	Yes	No

As verbs, alter is a hypernym of louden; that is, alter is a word with a broader meaning than louden:

Other hypernyms of louden include change, modify.

louden (verb)	alter (verb)
cause to become loud	remove the ovaries of
become louder	become different in some particular way, without permanently losing one's or its former characteristics or essence
	cause to change; make different; cause a transformation
	insert words into texts, often falsifying it thereby
	make an alteration to