Delta Brain Waves are the brain’s slowest frequency range cycling at a rate of 1-4 times per second (e.g. 1 Hz – 4 Hz). Delta Brain Waves become active in your brain when you are in the deeper stages of sleep (e.g. stage 3 and stage 4). They are associated with being completely unconscious. Delta Brain Waves have been known to oscillate throughout all parts of the brain and are not usually synchronized. Of all brainwave ranges, the Delta Waves have the greatest amplitude and are responsible for the slowest form of mental processing.