Standard piezoelectric transducers in a fixed parabolic arrangement radiate around 7 W of power at 40 kHz. Since sound waves carry momentum the paper leaflet is deflected when we move it over the focus.
This was part of a demonstration of Ultrasonic, audio technologies ltd.
Please see
http://www.tablix.org/~avian/blog/archives/2011/05/tangible_sound/
and
http://www.ultrasonic-audio.com
Very neat!
ion010101 8 months ago