"Penury" wrote in message
et

(quoting http://world.std.com/~griesngr/intermod.ppt )

"All commercial recordings tested by the author as of 6/1/03 contained
either no ultrasonic information, or ultrasonic harmonics at levels
more than 40dB below the fundamentals."

It is pretty easy for people to demonstrate to themselves that ultrasonic
components of natural sounds aren't audible even when they are at higher
levels than the fundamentals.

" Even assuming ultrasonics are audible, loudspeaker directivity creates
an unusually tiny sweet spot, both horizontally and vertically."

Most loudspeakers have response that rolls off very rapidy above 16 to 25
KHz