yes you are right,
there is drop of about 4-6db for 16khz,17,18, 19 and 20khz using my spl meter.
These high pitch sound are pretty hard to pick up. Only when u r really paying attention or with your ear near your speaker then will u notice that it is there. in fact 22khz can also be heard if my ear is near the speaker. I suppose my hearing is still good.
