Understanding accents/background noise edit

Thanks for responding to my question on the ref desk. I was particularly interested in your response because I had an audiogram when I was in my late teens/early 20s (about 18-20 years ago) and my hearing seemed to be fine (I actually had a very rude remark from my doc about wasting his time when he got the results) but I've struggled with understanding/defining 'noises' since I was a teen.