I was 23 or 24 when I first realized that my right ear didn't hear as well as my left one. One afternoon, I was sitting a few meters from an open window studying for an upcoming exam. I noticed that I could hear the sounds coming from the outside better when my left ear was facing the window than otherwise. I figured as long as I intended to keep studying, it was best to have my right ear turned to the window.
It's been more than 20 years since, and fortunately, my hearing hasn't deteriorated as far as I can tell. I suspect it is a genetic condition, for not only was my father somewhat hard of hearing too, but his sister was half-deaf; when we spoke to her we would be practically yelling and even then she could not understand many words.
Late yesterday afternoon I was out on my deck enjoying my solitude with a glass of beer and some reading material when these male and female Northern Cardinals (Cardinalis cardinalis) showed up. I rushed inside to get my camera and luckily, they stayed.
I could barely hear their high pitched (to me, at least) chirps that one bird book calls a "sharp chink". So, on a scale from a pin hitting the floor to the thunder of a lightning hitting my roof, the limit of my hearing is at the Cardinal's chink level.