Wow man, this is some serious sound you got there. Very cool. I like your room setup! ::clap:: :mrgreen:

[attachment=1]LotsOfAudio.jpg[/attachment]
*Yamaha DS2416 (pro recording and processing card)
*Yamaha SW1000XG (pro synthesizer card)
*Yamaha YMF719 (DOS games and awesome synthesis power)
Also cost a fortune when these were new, except the YMF719 which is a low end card with semi pro equipment quality. Yamaha rules !

[attachment=0]SoundOutputAndMore.jpg[/attachment]
*Modified Amfiton U-101 amplifier, 2x 80W at under 1% THD
*Slightly restored Amfiton 50-AS022 speakers, 50W at 4ohm (150W max), 20Hz to 25000Hz
*Priboi E-018 equalizer
That is soviet HiFi gear, cost a fortune when they were new ^^

...but I don't have any microphone, not a decent one anyway that can pick up those inaudible sounds :P
And such inaudible sounds can still be picked up my level meters, and if security matters you have those anyway in the premises. Alternatively you can push those sounds into the air yourself, but there may be health issues associated with it...

[quote="TmEE"]...I do however....[/quote]
I would love to read up on what you use as a sound system if you have anything special or even some pictures would be cool (some hardware pr0n) because I have been looking for good speakers for a long time now. Well, good "cheap" speakers but I suppose they don't come cheap. :(

Currently, I got a pair of "[b]EDIFIER E10 EXCLAIM 2.0[/b] - 48 Hz - 20000 Hz - 18 W @ 6 Ohm per channel". They sound pretty OK for cheap speakers. Some small tweeking is needed with equalizer, however.

[attachment=0]1685099.jpg[/attachment]

Creepy, however it is only possible on good speakers that are HiFi grade and good sound cards that do not cut into the audible range. MOST people do not have such hardware. I do however....

http://www.pcworld.com/article/2068525/researchers-create-malware-that-communicates-via-sound-no-network-needed.html

[quote]...the proof-of-concept malware prototype from Michael Hanspach and Michael Goetz can transmit information between computers using high-frequency sound waves inaudible to the human ear...[/quote]