From the recording Sonic Spectrum: The Complete Collection
0.1-3Hz Delta range is known specifically for being an aid for reaching deep sleep, lucid dreaming, increased immune functions, hypnosis. Decreased awareness of the physical world. Access to unconscious information. Dominant brainwave in infants under one year old. This range normally decreases when we focus, but this doesn't happen when a person with ADD - delta waves actually increase when they try and focus.
Try it out for yourself, simply meditate, by clearing all thoughts from your mind and focusing on the tone.
You can watch the video at https://youtu.be/Kacr24Ckl-Q