The effect can take up to a half hour to work, and results very, the person has to be relaxed and comfortable. What one experiences is different for everyone. Myself have tried it and most I had was the sensation of falling and movement, nothing visual.
What is going on is blocking out the normal senses for the brain. Covering the eyes and using the red light allows the eyes to stay dilated, while listening to white noise or pink noise further puts the brain into a forced need to create activity with the sound and eyes open, this creates the different sensations or hallucinations that people experience.