Logically impossible
If the brown noise does exist it has to be felt not heard. You would need a very high quality sub woofer to recreate the right frequency. And the ipod can not produce this frequency nor is it powerful enough. To be honest the brown noise will not make crap your pants. But if done with the right equipment it will make your stomach feel funny. So if you spend any money on this app you are a fool.
R1tts about
Brown Noise