Hemi-Sync is a trademarked brand name for a patented process used to create audio patterns containing binaural beats, which are commercialized in the form of audio CDs. Interstate Industries Inc., created by Hemi-Sync founder Robert Monroe, is the owner of the Hemi-Sync technology.
Hemi-Sync is short for Hemispheric Synchronization, also known as brainwave synchronization. Monroe indicated that the technique synchronizes the two hemispheres of one's brain, thereby creating a 'frequency-following response' designed to evoke certain effects. Hemi-Sync has been used for many purposes, including relaxation and sleep induction, learning and memory aids, helping those with physical and mental difficulties, and reaching altered states of consciousness through the use of sound.
The technique involves using sound waves to entrain brain waves. Wearing headphones, Monroe claimed that brains respond by producing a third sound (called binaural beats) that encouraged various brainwave activity changes. In 2002, a University of Virginia presentation at the Society for Psychophysiologial Research demonstrated that EEG changes did not occur when the standard electromagnetic headphones of Monroe's setup were replaced by air conduction headphones connected to a remote transducer by rubber tubes, suggesting that the basis for the entrainment effects is electromagnetic rather than acoustical in nature.
Replicated, double-blind, randomized trials on anesthetized patients have found Hemi-Sync effective as a partial replacement for fentanyl during surgery. A similar study found it ineffective at replacing propofol however.
See also 
- Brainwave synchronization
- Binaural beats
- Mind machine
- Human enhancement
- Intelligence amplification
- Neural oscillations
- Evoked potential
- Event-related potential
- Induced activity
- Lucid dreaming
- Ongoing brain activity
- Robert Monroe
- Altered state of consciousness
- US Patent 3884218: "Method of inducing and maintaining various stages of sleep in the human being"
- US Patent 5213562: "Method of inducing mental, emotional and physical states of consciousness, including specific mental activity, in human beings"
- US Patent 5356368: "Method of and apparatus for inducing desired states of consciousness"
- Stephen Barling, "Cosmic degrees: Out of body at The Monroe Institute". The Hook. February 13, 2003.
- , "". The Effects of Hemi-Sync on Electrocortical Activity, Sadigh and Kozicky
- Kliempt P, Ruta D, Ogston S, Landeck A, Martay K (August 1999). "Hemispheric-synchronisation during anaesthesia: a double-blind randomised trial using audiotapes for intra-operative nociception control". Anaesthesia 54 (8): 769–73. doi:10.1046/j.1365-2044.1999.00958.x. PMID 10460529.
- Lewis AK, Osborn IP, Roth R (February 2004). "The effect of hemispheric synchronization on intraoperative analgesia". Anesthesia and Analgesia 98 (2): 533–6, table of contents. PMID 14742401.
- Dabu-Bondoc S, Drummond-Lewis J, Gaal D, McGinn M, Caldwell-Andrews AA, Kain ZN (September 2003). "Hemispheric synchronized sounds and intraoperative anesthetic requirements". Anesthesia and Analgesia 97 (3): 772–5. PMID 12933400.