I have something strange with the right ear which is triggered by the mid-upper registers at forte and above. Not sure whether is is the same as you have. It is a strange grating noise, distorting the sound. I went to the ear specialist last year but he could not find anything particular. All he could suggest is that maybe there were some of the bony bits grating aginst another. Or that is what I understood, I think he's a very good specialist but I found it a bit unsatisfactory. He suggested I'll have to live with it, and take care when music making. I have an coustic, and come to think of it, I also had trouble with this when playing with two string players earlier this year when they had loud pasages. Strange thing is that other sound sources or instruments (like the organ at full blast) do not give a problem.
I've had that weird, crinkly, metallic sound at certain pitches when I had an ear infection. Very hard to describe to someone who hasn't experienced it. It sounds like a kazoo being played in a plastic grocery bag filled with aluminum foil. So annoying!
I have my hearing tested annually (and I can play extremely loud) no damage so far; in fact, my hearing has gradually improved over the last 5 years for some reason. Perhaps it is more important to pay very close attention to what we are feeling as we're playing and adjust our volume accordingly (or just put the piano-top down). If damage is being done, there are often subtle signs, such as the aforementioned foreign sounds we hear in an injured ear.
Although I'm no expert, my intuition tells me it is much worse to expose sore, rather than well rested ones, to noise.