I can't pick out a voice in a crowded room, or indeed separate speech from any sort of background noise. In ideal listening conditions I miss words making sentences not make sense, and often I don't realize someone has started talking until I've already missed the first sentence. However I don't have any physical hearing problem. Each time I've gotten my hearing tested I've been told my tonal hearing is perfectly normal. Yet the problems I have with picking out and understanding speech are absolutely debilitating, and I can't get anyone to understand that it is a disability and that it is real.
At my insistence my audiologist administered a speech processing test, but I was nonplussed to discover this test is completely unrealistic and did not at all match the situations I have trouble with. The way it worked was that it would mix a perfectly clear speech track with white noise, or a repetitive loop of background speech or cafeteria noise. But since the sound streams were mixed together so artificially, my brain could separate the audio streams based on source track, words or no. And since the "interruption" loops were repetitive, my brain could learn the pattern and discount it. So of course I passed that test, too. The speech processing problems I have occur in real environments when executing functions of daily life.
In the end the audiologist told me that maybe my problem is that I have ADHD and that my attention isn't able to lock-on or stay with a conversation well. He didn't know of anyone in my area who treated adults with ADHD, but promised to send me a referral. I'm guessing he never found anyone, because that referral never came. However it eventually led to me getting diagnosed and treated for ADHD on my own. (Although it took almost 2 years to even get an appointment.) I've found that getting a diagnosis and medication for ADHD has improved my life immensely. However it has not helped with the original problem; I still can't separate speech from other noises.
I resonate with the commenter who says he thinks his undiagnosed (physical) hearing loss once contributed to him losing a job. At work, I find excuses to hide/disconnect my phone because I have so much trouble making out what people are saying over a phone. I use chat and IM, and write everything down or ask for things written down. Still, sometimes I'll miss or not understand some verbal instruction and get in trouble. It also causes relationship problems - so many misunderstandings, misheard words, doing the opposite of what my spouse asked or not realizing she said something to me. I avoid some social activities because I know that background noise there will prevent me from participating, or because mishearing people might lead to a social gaffe or a dangerous misinterpretation of safety instructions.
I can't read lips to get by, either - whatever it is in my brain that affects speech processing affects lip reading equally, if not worse, and sometimes when I'm receiving the "all circuits are down" message from my speech centers, I can't even understand someone's sentence no matter how many times they repeat it. But if they write it down on a note I can understand it. In a way, it's like the inverse of dyslexia.
Anyway, not that I have much hope of an answer, but anyone know where I can go to talk about it or what kind of doctor would be actually interested and not just brush this off?