To add to this, most middle age adults can not hear above 15khz and threshold is very high at 11khz, especially if they were exposed to high sound levels in you

To add to this, most middle age adults can not hear above 15khz and threshold is very high at 11khz, especially if they were exposed to high sound levels in youth. Virtually no one can hear above 22khz.. if you ever hear people saying they can it is most likely bs. People often tell stories about playing a sound or being in a lab etc. they think they heard above 20khz, but mostly likely what happened is whatever inevitable non-linearity exists in their playback chain acts as a mixer creating frequencies well in the easily audible range.