The words aurally, orally sound the same but have different meanings and spellings. Why do aurally, orally sound the same even though they are completely different words?
The answer is simple: aurally, orally are homophones of the English language.
with regard to sound or the ear
Pertaining to <xref>sound</xref> or the <xref>ear</xref>.
By means of the ear or of audition; in an auditory manner.
(of drugs) through the mouth rather than through injection; by_mouth
by spoken rather than written means
Spoken as opposed to written.
Definitions from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved., from Wiktionary, Creative Commons Attribution/Share-Alike License., from The Century Dictionary. and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.