When the subject is under hypnosis it is possible to order him to not “hear” some specific sounds, even after he is out of hypnotic sleep
When he will hear the sound , his consciousness will not be aware of at all.
It is required to record a speech, then to modify the record a lot with some electronic device to make the voice look like a waterfall
The voice must be dificult to understand , without attention it look like a waterfall.
Then under hypnosis the subject will be ordered to never hear at all all sounds like this.
Then the speech record is played later, while the subject is doing work for example. The speech words will be perceived at some inconscious level, but not at the consciousness level. The speech record must be played daily
Then the subject will start having sometimes some ideas similar to the speech records he was listening, but he will think the ideas come from him
He will start slowly going in a new direction without ever noticing someone is manipulating him.