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Frequency is properly the rate at which any periodic event repeats, but in light and sound machines it is used more specifically to refer to the primary rate of visual and auditory stimulation -- to the eyes, it is how fast the lights are flickering, to the ears, it is how often the sound is pulsed on and off, (pulsed tones) or how often the amplitude is modulated (binaural beats). Frequency, like pitch, is measured in Hertz. The frequencies of stimulation in light/sound systems are in the brain wave frequency range. Ganzfield is an effect discovered by German scientists in the 1930s, in which the eyes are exposed to a totally uniform visual field, with no edges, color changes, or movement. This can be achieved by looking up at the sky on a clear, cloudless day, or with very specially constructed illuminated glasses. The circuitry in the brain that is constantly scanning the visual field for edges and movement finds absolutely nothing, and shortly shuts visual sensation off, as the eye responds primarily to changes. Soon the subject cannot tell if his eyes are open or closed, and altered states of consciousness result. Light sound glasses with the lights left on have sometimes been advertised as "ganzfield", but the effect produced by this technique is definitely not true ganzfield or even close. Gentle on/off refers to starting a session by slowly ramping on the sound volume and light intensity, and ending a session by slowly ramping them back off. This feature makes the transition into and out of a session more pleasant, and prevents sudden jerky endings that can destroy the effect of a session. Hertz used to be called "cycles per second", meaning the number of times a repetitive event occurred per second. Then someone noticed that physicist Heinrich Hertz (1857-94) had no measurement unit named after him, so he was appropriately immortalized, giving opportunities for bad puns: Crank up the frequency till it Hertz. In sound, Hertz is probably number one, but amplitude is a close second and tries harder. History The effects of flickering light stimulation have been known for a long time. Ancient shamans knew that flickering light could induce altered states of consciousness. Around 200 A.D. Ptolemy noted that the flickering of sunlight seen through the spokes of a spinning wheel could cause patterns and colors to appear to the observer, and could produce a feeling of lightheadedness and euphoria. In modern times, (1940's and 50's) neuroscientist W. Gray Walter used a strobe light to create flickering light stimulation, and noted that the brain wave pattern of the whole cortex was changed, not just the area associated with vision. Experimentation in the 1960's and 70's showed that adding pulsing sound enhanced the experience. The invention of the microprocessor made it possible for inexpensive light/sound devices to be produced, and hundreds of thousands of people have tried them. Some of the above was extracted from Megabrain, Michael Hutchison. Intensity refers to the brightness of the light stimulation. Just scale is a seldom used musical scale that has seven notes per octave, and is designed to make chords relative to the base of the octave come out right. The Just scale produces "clearer" dual binaural beats. Thus a better chord is produced. The integer pitches of the Just scale make integer binaural beat offsets work better. (With a pitch ratio of 1.059 you don't get many integer pitches). See also tempred scale. Light frames or Stimulation Glasses are eyeglass frames with light sources mounted inside in front of the eyes. The lights flicker on and off during a session at the stimulation frequency. Mind Machines is a generic term for light and sound machines. The term brain tuner is also interchangeable for this technology. An AVS is a device that influence your state of mind using specially designed light and sound stimulation. Flickering lights and pulsating sound have been used for centuries to influence moods, from music for relaxation to adrenaline-raising dances around the tribal fire. Light/sound systems have the advantage that the stimulation is more controlled, better designed for its purpose, and you don't have to hire a band. They are very effective relaxation tools, a good assist to meditation, and can aid the learning process. Octave is a interval between notes that has a 2/1 frequency ratio (e.g. 220 to 440 Hertz). In the tempered scale there are 12 total notes in an octave, seven "white key" or natural notes and five "black key" sharps and flats. The name octave comes from counting one too many white keys, or maybe because "heptave" just doesn't sound good. Phase is the timing relationship between the different stimulation channels --the two eyes and the two ears. When pulsed sounds are selected, there are six phase settings available.
Pitch refers to the frequency of sound stimulation, and is perceived as "low notes" (bass) to "high notes" (soprano). Ramping refers to changing a stimulation parameter gradually so that "jumps" are not perceptible. Most light/sound systems can ramp frequency, Musical scale refers to the way in which particular sound frequencies are picked as the notes to be used in playing music. An octave is a musical interval with a frequency ratio of 2/1 (e.g. 220 to 440 Hertz). Different cultures and musical traditions have used many different ways of dividing an octave. Western (this is Western as opposed to Eastern, not Country Western) music is mostly based on the tempered scale, with 12 notes per octave and equal frequency ratios between adjacent notes. Sessions are programmed sequences of changing light and sound stimulation, designed for a specific purpose such as relaxation, alertness, sleep, etc. Sessions typically last from 15 to 45 minutes, and some systems allow the user to vary the running time. While a session is running, the session programming controls most of the operation of the system, although some features may be left to operator control. The variety and quality of the built-in sessions on a light/sound system has a profound effect on how well the machine will work for you. Sine wave sound refers to pure tones consisting of a single frequency. When you play a musical instrument, the notes have a fundamental frequency and many harmonics. The result is not a sine wave, but on most instruments the result sounds pleasing. On a light/sound system that does not have sine wave sound, the alternative is usually square wave sound (on or off), not because it sounds good (it doesn't) but because it's easy to make on a computer. Mixed tone beats and binaural beats don't work as well on non-sine-wave sound either. Soundscapes is a name commonly referred to digital "nature sounds" recording in products such as baby room soothing sounds devices, general background sounds devices and sometime alarm clocks. A small nature sound bit (rain, forest, ocean, waterfalls etc.) is recorded on a chip and repetitively played back. The Sharper Image recent introduction was such a product with added glasses that increased/decreased the intensity in a smooth pattern. Although nature sounds are not designed with certain frequencies in mind, the repetitive sound and light pattern are soothing and work well for quiet entertainment. Surf is a mixture of lots of pitches -- the synthesized surf sound in some mind machine systems is an approximation to pink noise (random noise with equal energy in each octave), cut off at about 1000 Hertz. Tempered scale is the musical scale used in modern western music. There are twelve notes per octave with a constant frequency ratio between adjacent notes (the twelfth root of 2, or about 1.059). This approach has advantages in playing music in different keys, but does not make chords come out as well as they could. An interesting alternative is the Just scale used in some light and sound systems. Tone refers to the type of sound stimulation used. Pulsed tone - sine wave tone at the
selected pitch, pulsed at the selected frequency, with the selected duty
cycle. Alternating tone/surf
- the above two
tones, alternating in each ear. Visuals refer to the shifting, colored patterns perceived when you look at the flickering lights on a light sound system. The patterns are optical illusions caused by the interaction of the flicker rate with the sensing and processing rate of your eyes and brain. You may have seen a child's top with radial black lines, that when spun, gives the appearance of changing colors. That is a similar effect. The visual images from a light sound system can be very impressive and contribute a lot to the enjoyment of using the system. A session that creates a good light show is imaginatively said to have "great visuals". Volume refers to the loudness of the sound stimulation.
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