My hearing is just fine, so before I was diagnosed with Asperger's nobody understood why I constantly asked people to repeat what they said several times for me to understand it. In addition I would drive my parents nuts when I would turn up the TV volume when they started talking in the kitchen.
Turns out this is par for the course for Central Auditory Processing Disorder (CAPD), a condition common among autistic people in which the in-brain processing of speech is out of whack, resulting in unusual difficulty in understanding speech in many situations. I had the misfortune of often accidentally offending people who are not native English speakers and have a strong accent because my problems understanding them were taken the wrong way (and my typical aspie issues with non-verbal communication just exacerbated the incidents).
Incidentally this has become a big problem with my attempt to learn Spanish. I have the basics of the grammar down, but understanding speech is almost impossible.
Related to this is that I have great trouble understanding complex directions given to me orally, I much prefer them to be written down.