To put one of the contentions made above into the right perspective:
Experiments have shown that it is true of course, that you can hardly HEAR above 20khz and then only in your younger years. But subjects listening to MUSIC have complained of "something missing" in its representation, when everything above 20 khz was sharply cut off, even though they could not hear over 20 khz in an electronically induced single tone sweep from 20hz to 50khz. Unfortunately I have forgotten, where these findings were published. But the experiment, which has been repeated several times in different places, is quite well known and its findings are practically common knowledge by now.
Experiments have shown that it is true of course, that you can hardly HEAR above 20khz and then only in your younger years. But subjects listening to MUSIC have complained of "something missing" in its representation, when everything above 20 khz was sharply cut off, even though they could not hear over 20 khz in an electronically induced single tone sweep from 20hz to 50khz. Unfortunately I have forgotten, where these findings were published. But the experiment, which has been repeated several times in different places, is quite well known and its findings are practically common knowledge by now.