Might be long, but hopefully relevant to someone who may be experiencing something similar.
About 6 months ago I woke up with a feeling of "stuffiness" in my left ear. Kinda felt like my ear just needed to pop, so I wasn't too worried about it at the time. 2 days later when it still hadn't gone away was when I got a bit annoyed, it's also when I started to realize that my hearing wasn't quite right.
I went into see an ENT for an auditory test immediately, at which time I found out just how bad it it had gotten. I had moderate/severe mid to low frequency hearing loss in my left ear, and the frequencies I could hear were pretty distorted, (almost like Charlie Brown's teacher). Side note: If anyone is interested, I can post the original audio test that I had done. Anyway, the doctor then went on to tell me that the type of hearing loss I was experiencing was most likely due to nerve damage in my inner ear and permanent....FML.
They thought I may have Meniere's disease due to the ringing and frequency loss i was experiencing, so I was put on steroids for a couple of weeks. During that time there were a few days when my hearing completely returned - low frequencies had come back, the ringing stopped, and the distortion had gone away. Then, just as quickly, my hearing would get worse again and the ringing would return. After a few different medications with the same results (seemingly random periods of better hearing) I started doing some research and paying more attention to what I was doing and came to the following conclusion.
Diet and Exercise - My particular problems SEEM to stem from a build up of fluid in the inner ear. I noticed that after I got a good sweat doing, my hearing would get better rapidly. Reducing the salt in my diet (since it causes you to retain water) combined with exercise has pretty much brought my hearing back to a normal level. To make sure I hadn't just gotten "used" to the reduced level of hearing I went back to get another audio test done and it confirmed that my hearing had indeed returned, the doctors were actually pretty shocked.
Not everyone's case is the same, but since I know how frustrating it can be, I'm hoping that it may help someone. After visiting numerous doctors, not one of them mentioned diet or exercise as a possible treatment, so you might want to check into it if you haven't already.
tl;dr - My ringing and frequency loss is under control by watching what I eat (low sodium) and continuing to exercise regularly.