When I listen to the ultrasonic on my speakers I always hear a high-pitched noise (like a ringing in your ear if you turn it up too loud), I've gotten used to it though so I barely hear it. Ryan, are you sure it isn't your speakers? They have to be 20khz frequency response for ultrasonics.
http://subliminal-talk.com/showthread.ph...light=ipod
http://subliminal-talk.com/showthread.ph...light=ipod