I wanted to test if the 18,98 Hz Frequency would strike fear into my guests at home. Your first ignorent First Test() will fail:
That was a stupid approach for creating InfraSound!
Sound that falls just helow the human hearing range (20Hz) at about the frequency of 18,98, strikes fear into people e.g. ghost houses have these frequences (they led to e.g. a new fan causing unhearable sounds).
So… I will need some specific hardware (e.g. special subwoofer like http://www.rotarywoofer.com/), possibly a new sound card (did not even check yet) and probably a specific sound .dll for coding against to experiment on my guests (see also: http://forums.makezine.com/comments.php?DiscussionID=3023 and here: https://sites.google.com/site/appliedbiophysicsresearch/sound/infrasound/infrasound-design)
To measure this I will also need some very good microphones.
This is an interesting lab experiment for the Ed-Lab, @todo