Getting into Transcendental meditation without mantras is possible.
What I did to get into this state of meditation is by experimenting with the wake back to bed method.
I meditated for 30 mins I went to sleep and started dreaming with my spirit companion.
I woke up walked around and started meditating for another 30 minutes but only did 15. I entered sleep paralysis my spirit companion was in the form of a floating black diamond. The diamond was dark black compared to my candle lit room. I saw another energetic field around that floating black diamond pulsing with dark energy.
While in sleep paralysis I was getting visuals of the dream I had while meditating. In this dream visual I tried to hid under my covers 
. From my trance state I consciously heard her voice say “why are you hiding from me.”
I then fell back into the dream.
This was strictly being playful!
Analyzing what I did in meditation my thoughts became relaxed and quiet. Almost to the point I couldn’t hear them. Really the only thing I heard was whispers of thoughts that weren’t mine. A demonic presence was putting me in theta causing trances. Bouncing in and out of dreams and sleep paralysis.
In Transcendental meditation you do not need mantras from instructors.
You can use frequencies natural and unnatural to get into Transcendental meditation and (theta).
Also frequency of entities do make nosies sometimes I hear and feel them. Picking up on theses waves of energy subconsciously is scientific which is why my claim works.