After a hearing test, I asked for the graph of my hearing freq, vs. amplitude... Interestingly enough I was using a 670 HZ sidetone... I had a HUGE dip right at 650... I moved my sidetone to a small peak at 510, and was able to copy CW much better, faster, and more relaxed...
It's pretty easy to test your own hearing that way if you have an audio signal generator. I did this once, and don't recall the results. Maybe it would benefit all of us to do that.
According to the above test, I have good, normal hearing... According to an actual test performed by a medical facility, I don't... My guess is that the heart of the online test above is how you answer the questions, not what you hear...
This test may be better: http://newt.phys.unsw.edu.au/jw/hearing.html Read the warnings and instructions carefully first, though.
Noise from a receiver front end and outside noise from man made or natural sources isn't pure "white" noise of all possible frequencies together but more of a "pink" noise that is weighted to the higher end of the audio spectrum. At least here in my station equipment, receivers, speakers and headphones.. I tend to tune filters to peak, and tune the CW notes in the lower region of the audio spectrum to bring a desired CW signal out of that noise . Maybe this is partly due to my older ears aging and failing in the higher region of the audio range , as well ! I don't quite understand the "lower frequency artifacts" you are hearing. Again, it varies from person to person , I'm sure .
Congenital hearing deficits in both ears, and getting worse as I age. Lower pitched sounds (including male voices) are especially difficult to understand. The hearing defects are not remediated by amplification--in fact, loud, shrill sounds hurt my ears. A higher pitched sidetown is an absolute necessity for me.
The hearing aides today use sophisticated filters and are a lot better than those "amplifier" types of years ago...however they are expensive.
