And why is that?
One day in class while taking a test the teacher started playing test tones from 20khz down, I noticed it at 18k, and slowly the rest of the students heads popped up wondering what it was. Got down to 12k, and one kid was still on his test and the teacher asked him if he heard that noise and he had no idea what was going on.
Anyways to the point, there were several kids with high 140 systems in class and the kid that didn't look up was the hood ninja from Miami that had 4 6x9s in the back, super annoying, high pitched speakers all over.
I believe the high fq at higher dBs are more dangerous than low fqs.