I try to convert understandable state through “Change Pitch” effect but I couldn’t do it.
In addiction,I analyze Nyquist Promt code about Silent Subliminal message but I couldn’t do it.Because,I think that If I understand that normal file to ultrasonic file, I understand that ultrasonic file to normal file, too.
If Change Pitch didn’t work, then it may have been made with one of the modulation techniques which means you need to know how it was made in order to decode it. There’s no easy way to guess at it.
Not all subliminal techniques are reversible. If it is reversible, you’d have to know “the secret”. If you don’t know how, it’s like cracking a code or solving a puzzle. The ability to decode is “nice” because you can prove there is a actually a “hidden message” but that’s not the point… You’re not supposed to hear it!
Was the “original” file MP3 or did you make the MP3? MP3 tries to throw-away sounds that you can’t hear so any subliminal information may have been filtered out.
You’ll also loose information by simply pitch-shifting unless you also increase the sample rate. The audio is limited to half the sample rate. For example, audio CDs have a sample rate of 44.1kHz so they can’t contain audio above 22,050Hz.
For speech you need a frequency range of about 300Hz to 4000Hz (or more). The main voice frequencies are in the lower-part of that range. Let’s say you multiply by 50. That brings 300Hz up to 15kHz, but it brings 4000Hz up to 200,000Hz which is out of the range of any normal audio format.
So… If you simply pitch-shift up (by a lot) you’ll loose information, and if you pitch back down again it will be unintelligible.
When pitch shifted, it’s not very interesting, and there is nothing intelligible. Here’s a short sample from your file:
It’s possible that there may be speech encoded into the ultrasonic audio in some way, but without knowing how it has been encoded, and more importantly how to decode it, it is just noise.