This file is designed to help you determine whether or not your speakers meet the minimum requirements for playing our ultrasonic subliminals, which require a minimum upper frequency response of 20 kHz from your speakers.
If you can play this 30 second file all the way through and hear the sound rise in pitch through the whole 30 seconds without hearing statc, crackling, or anything but the sound (or apparent silence, as most people will hear after about the 20 second mark), your speakers pass muster for playing the ultrasonic subliminal formatted tracks.