oral, aural

Oral or oral means by mouth, or by speaking--
She's afraid of needles; do you have an oral vaccine?
He'll need oral surgery to have his wisdom teeth removed.
Will the exam be written or oral?

Aural or aural ( rhymes with oral ) describes something related to the ear, or to the sense of hearing--
His hearing loss was caused by the complications of an aural infection.
The doctor thinks that aural surgery might improve his hearing.
An aural exam will determine the extent of hearing loss.
Music students may be asked to take an aural test, to show that they can hear the difference between notes.

Now that you know that, you can say--
"He asked for a written test, because his aural damage made the oral exam so difficult."