I don't think that is a problem. One could think that if someone doesn't hear sounds above 17 kHz then they lose 3/20 = 15% of sound spectrum but in fact they j

I don't think that is a problem. One could think that if someone doesn't hear sounds above 17 kHz then they lose 3/20 = 15% of sound spectrum but in fact they just lose a small part of the highest octave (from 10 octaves total) which is about 5%. In most cases those high frequencies contain only overtones from lower frequency sounds. The hearing can really get worse with age, but definitely not because of beeiong unable to hear highest frequencies.