The nuances of audio subliminal presentations are widely varied. One process involves “time-compressing” the verbal message by either speeding up the human voice to a high-pitched squeal or by digitally compressing the words, which involves removing the spacing between the sounds which results in one continuous noise.
And if everything is clear with the increase in the audio rate, then how to make digital audio compression to a noise state? Respectfully…!
Sorry, I don’t understand your question…
. One process involves “time-compressing” the verbal message by either speeding up the human voice to a high-pitched squeal
The audio signal is limited to half the sample rate so as you increase pitch you loose the highest frequencies (information permanently is lost) and if you go too far with this (depending on the sample rate) it will become unintelligible (even when returned to the correct speed).
which involves removing the spacing between the sounds which results in one continuous noise.
If you just remove the spaces between words it generally won’t become unintelligible (so it’s not subliminal) and you’d have to save a table of spaces/timing if you wanted to restore the sound.
And if everything is clear with the increase in the audio rate, then how to make digital audio compression to a noise state?
What? There are lots of ways to add distortion or noise or otherwise mess-up the sound. Some are reversible and some are not.
…If you mix low-level speaking with noise (or music) the music will drown-out the speaking. And, as long as you do it correctly and save the music/noise it can be subtracted-out so you can hear the speaking again. It’s probably more “fun” if you use a reversible method so you can prove there is a hidden message.
The nuances of audio subliminal presentations are widely varied
And they are all pretty-much equally (in)effective. 
…I saw a program on TV once about “how perception works” (or something like that). It wasn’t about subliminal messaging but one thing they did was show people a picture of the Mona Lisa for a few seconds. There was something added that didn’t belong in the picture (maybe a UFO in the corner). If the person didn’t notice it, that information never got into their consciousness and no matter how hard they tried to remember or if they were hypnotized, etc., they couldn’t remember that something was unusual about the picture. If you don’t notice something, or if you’re not paying attention, that information never gets into your brain…