Ganzfeld effect

The Ganzfeld (from the German, meaning “full field”) effect describes the state of sensory deprivation achieved by flooding one of the senses with a constant uniform signal. Once the constant signal floods the particular sense, the brain stops registering the differentiation and the result is an absolute deprivation of that particular sense. Used for meditation, parapsychology. [google]

Short blog article and Ganzfeld goggle HOWTO. Another, similar guide for a visual Ganzfeld device.