OK, I’m 66 and have hearing loss. I don’t hear anything above about 2700hz. So just making frequencies above that LOUDER doesn’t help me.
So what I want to do is compress the frequency range 5000-8000hz into a range of 2600-2700hz
and not change anything below 2300hz. I tried to use audacity to just select frequencies that are between an upper limit and lower limit and the use ‘change pitch’ but it didn’t work. The ‘change pitch’ was applied to the whole file and not just the parts that were within the upper and lower bounds I chose.
An interesting idea, but I don’t think this is going to work.
I don’t know of any effects that can “compress” frequency bands in the way that you describe. I can “pitch shift” frequency bands in a similar way to what you describe, but the result is a confused and muddy mess.
I think a better approach would be to just play with the Equalization effect (“Graphic” mode is probably easiest). Turn down the frequency bands that you can’t hear. Turn down the very low frequency bands as these contribute little to ineligibility, then turn up the higher frequencies that you can hear and tweak the settings for whatever sounds best to you.
While adjusting the Eq, keep an eye on the playback meters so as to keep the level below 0 dB (and so avoid “distortion” / “clipping”).