THIS DREAM AGAIN, DEJA VU!
Between sleeping and waking, brainwaves (the rhythmic pattern of neural activity, which oscillates in waves) are in what’s known as “theta”, waves between four and eight Hz. This frequency is also measured in meditation, hypnosis, and sensory deprivation. In the lattermost of these, subjects report an increased in creativity and problem solving, while the benefits of meditation go without saying, as does the power of hypnosis.
This manifests in what’s known as the Ganzfeld Effect where hallucinations occur - similarly to their emergence in hypnagogia, where theta waves occur. What’s interesting is, for anyone who’s had extensive experience with sensory deprivation, the emergence of the Ganzfeld hallucinations is that of slow development. The everyday noise of the busy mind (what meditation is attempting to quiet) slowly clears, slowly forms into more coherent images of thought. As one lays in sensory deprivation longer, the static noise of the mind clears, like a turbid pond left to settle, a signal slowly forming clearer and clearer as time goes on. This is the emergence of that other state of consciousness, theta waves, similar to how experienced practitioners of meditation can induce the same in their own minds. Sensory deprivation however, allows for both this to be induced by technique, rather than training, but also allows those who are trained to use the technique to greatly enhance their practice - something done in Tibet in what’s known as a “Dark Retreat”.
While a float tank is obviously the best option, as it allows for full-body deprivation, this isn’t always the best solution. For private individuals it can be very expensive to purchase one for unlimited use, and making appointments at companies offering it as a service is rather cumbersome and cannot be done in nearly enough frequency. For this reason, it’s imperative that one develops a technique for sensory deprivation with no equipment.
Touch & its accompanying sense, that of the body’s general spatiality cannot be eliminated, however it’s vital that the body not be a distraction. Sit or recline on a firm surface - a wooden chair, the floor, or a firm couch, in a position where you are completely at ease, on your back, without imbalances or contortions. This allows for the body to vanish as the deprivation goes on, with the ultimate goal being to forget your body entirely.
Sound and vision remain as the other two most potent senses (and ones that could disrupt you, unless you are attempting this in a kitchen or someplace else with extreme odors) which must be blocked out. Vision can be blocked out with any sort of blindfold, though I would recommend investing in one specifically, the silk eye masks people use for sleep - they’re well worth the minimal investment. Sound however, opinions vary on. While most people would default to active noise cancelling, my advice is to use both active and passive noise cancelling. A bit hard to find, but there are options for ear protection headphones, of the sort used in operating machinery, that come with built-in speakers. This will deafen most sound, however it’s not enough. Plenty of sound will still leak through, which must then be actively cancelled, via a noise field. I personally use pink noise with a cut-off filter at the high end to reduce it to a nice medium tone around where you would hear human speech and everyday noise.
There isn’t quite a “wrong way” to do this technique, except cutting it short. It takes at least ten or twenty minutes before the brain begins to change state in any meaningful way, longer if you’re truly seeking to go deep. Time passes at first excruciatingly slow, and then strangely, thus the only remaining word of advice is to not give into impatience.