Basics of Flickering Light & Pulsed Sound Brain Signaling


The primary feature of certain devices is the “photic driving” of “flickering light” stimulation. This effect falls into the larger category of neuromodulation. In some, but not all, devices, the “flickering light” is combined with various sound-based pulsing stimulations.


Our brain is always seeking the “signal in the noise.” It prefers to organize ongoing sensory stimulation into patterns for easy recognition later on. Having a library of patterns makes predicting future responses easier and faster. In a sense, our brain is “always jumping to conclusions.” Hopefully, these predictions are correct. However, sometimes the predictions fail to be accurate…and our brain must change some old patterns for new, more effective patterns. Call it Change or adaption or learning or growth. In any case, it is very important to build positive patterns (habits), and it is equally important to be able to change to better new patterns when change is necessary. Technically, this “dance” is known as the “stability/plasticity dynamic,” – and we must be good at both.


Brain Entrainment:

Originally discovered in the late 1930s, this phenomenon was called the Frequency Following Response (FFR). Lacking sophisticated technology and lack of motivation, the FFR remained dormant until the 1960s-70s. At that time, FFR was renamed Brain Entrainment. Brain Entrainment recognizes that when stimulated with regular and repetitive light or sound (and others such as electricity and magnetism) signals, the brain will begin to produce electrical brain waves in the same frequency. Neurologically, Brain Entrainment is primarily a “top-down” organizational process based on prediction and pattern recognition. To entrain the brain, research has demonstrated that the process generally occurs in two stages:


  • In which the stimulating signals impose or “force” themselves upon the brain;
  • If the signal stops during this stage, typically, the brain also stops generating these signals;


  • This second stage is when the brain begins to produce the stimulating frequency on its own and may continue for some unpredictable time (usually short) after that;
  • To reach actual entrainment, typically, the regular repetitive stimulating signal must be sustained for at least 6 to 8 minutes in the “superimposition” stage.
To successfully entrain the brain to a certain frequency, the signal must maintain its regular and repetitive pattern – variations, interruptions, and clustering of the signal rapidly diminish the superimposition and entrainment process. There are different types of entrainment signals – each has its characteristic features:

Light Signals:

Isochronic Light Signals:
“Isochronic” means “same (iso) timing” (chronic); This regular timing creates the “flicker” effect; Each “flicker” can have a different “shape”;
  • Smooth sine wave;
  • Rigid square;
  • Sharp triangle;
  • Offset sawtooth.
Each “flicker” can also have a different “duty cycle”;
  • The “On” and “Off” can vary;
  • For example, the ON can be 90% of the energy, and the of can be 20%.
By choosing variations in the rate of the isochronic “flicker” (e.g., 15 Hz), the type of signal shape (e.g., square wave), and the duty cycle (e.g., 80/20), the quality of the light signal can be extensively modified.

Sound Signals:

There are two main types of sound signaling for Brain Entrainment:
As mentioned above, the sound signal is highly regular; The shape can also vary;
  • Smooth sine wave;
  • Rigid square;
  • Triangular;
  • Sawtooth;
  • Others are less used as well.
The sound signal can also have variations in pitch or tone; The sound signals can also have variations in volume.
Binaural sound signals are created differently than isochronic signals; Isochronic sound signals are created “outside the head” and heard through the ears; Binaural sound signals are created “inside the head” in a special way; To create an “inside the head” binaural signal, you combine two separate tones – one tone (A) goes into one ear, and the other different tone (B) goes into the opposite ear; The difference between tones A and B is processed “inside the head” to produce the resulting tone (C). Example:
  • Tone A is 10 Hz;
  • Tone B is 15 Hz;
  • The resulting tone C is heard as 5 Hz
Importantly, the “spread” between tone A and tone B is limited to produce a tone C; When the “spread” is greater than 20 Hz, the resulting tone C gets weaker – at around 35 Hz, the tone C basically disappears – your brain cannot process the difference in tone A and B; In brain wave signal generation, there is a small frequency range around 35 Hz that is called the “Frequency Fusion Rate,” in which the flickers appear to “blur” into one merged signal; Consequently, claims of a binaural-generated 40 Hz gamma signal are not correct.
Isochronic vs. Binaural Sound Signals:
Binaural sound signals were identified in the early 1970s; The Brain Entrainment effects of isochronic signals are much more effective than binaural signals. Binaural sound signals are recognized as the weakest form of sound signaling for achieving Brain Entrainment; Despite being much more effective in inducing Brain Entrainment, isochronic sounds are not as popular because they require a higher level of compositional design – otherwise, the isochronic sound can be unattractive and even irritating to the average user; Binaural sound signals are used extensively because they are very easy to insert into any other sound file and produce a low-profile tone without having any competing and distracting sound – they are not used because they are so effective but instead because they are unobtrusive while still permitting the manufacturer to claim of including “brain entrainment” in their sound source.
White, Pink, Brown Noise:
In Brain Entrainment, various forms of “noise” can be used to reduce distraction; These “hissing” sounds can be very effective in submerging the listener in a sonic “envelope”; Such types of “noise” are common in “white noise” devices that block out disturbing sounds and can be found in many sleep aid products.
Composed Music:
Initially, using attractive composed music (inmany different forms) can seem appealing; The drawback is that because our brain is highly (even irresistibly) attracted to regular and predictable patterns, non-integrated music used as sound for Brain Entrainment can enormously diminish the “Frequency Following” response to “driver frequency” in the signaling (this is especially true when the music is running parallel to flickering light signals) – this “pattern competition/conflict” is found in many soundtracks that attempt to use subtle binaural sound signals mixed into rhythmic musical compositions.

Random Signaling:

Essentially, Random Signaling is the opposite of Brain Entrainment. In Brain Entrainment, the signals form a highly regular and predictable stimulation that is the core feature of the Frequency Following Response. In Random Signaling, the signals are highly irregular and resist patterned predictability. Neurologically, Random Signaling is primarily a “bottom-up” infusion of noise stimulation that lacks any message resolution or opportunity for integration. Oddly, some manufacturers using Random Signaling will claim that the process is a Brain Entrainment effect when it is absolutely not because it lacks all elements of the Frequency Following Response. Random Signaling with flickering light tends to destabilize foundational brain signal processing with a resultant “dissociative” subjective mental state. The dissociative state will generally be experienced as an odd “floating” or featureless feeling which can be mistaken by the inexperienced as a form of meditation. In short doses, Random Signaling can be productive in reducing stressful or rigid patterns of mind, although the subjective reaction for some people can be disconcerting and uncomfortable. If Random Signaling is experienced too often and/or for regular extended periods of time, the initial dynamic visual displays of colors and geometric patterns can dissolve into featureless two-dimensional shades of gray as a result of protective neurological inhibition in the visual cortex of the brain. The brain seeks protection from the sustained stressful “light noise.” It has been noted that similar protective visual inhibition has been displayed in individuals suffering from PTSD and/or nervous exhaustion.

Brain Engagement:

Brain Engagement is a new and advanced form of neuromodulation that targets a style of brain signaling designed to trigger and guide positive neuroplastic changes in the brain. In the 1970s era of Brain Entrainment, there was no awareness of the normal capacity for the adult brain to develop new and positive neuroplastic changes. In simplicity, Brain Entrainment reinforces basic patterns through predictable repetition, and Brain Engagement stimulates and guides the generation of new adaptive patterns in the brain. Brain Engagement brain signaling is “compositional,” which means it uses different types of signaling within the light (and sound) experience. The signals in the composition will shift from attention-getting destabilization to well-patterned messages, to short periods of conflict, to reinforcing returns to the vector or theme of the composition. Neurologically, Brain Engagement is primarily a structured “bottom-up” multi-sensory stimulation with secondary elements of periodic “top-down” integrative messaging. Brain Engagement, to activate neuroplastic change in the brain, employs “surprise” or “predictive error” elements to excite the selective attentional states mandatory in any neuroplastic method. The “attentional state” required for initiating a neuroplastic response is completely absent in Brain Entrainment methods – the Frequency Following Response and the accompanying highly predictable signal repetition results in the brain not having to “pay attention” and hence, no trigger of change. Brain Engagement also employs the “marginal demand” element required in any effective neuroplastic method – the experience must be just a tiny bit more than your everyday comfort level – this “tiny bit of demand” helps trigger the core changing dynamic to positive neuroplastic brain change. Brain Engagement also has an intrinsic theme (technically, a “vector”) that moves the messaging towards a certain “probability state” – beyond the oversimplified concept that a single brainwave frequency will result in a specific subjective mental state, the vector provides a kind of neurological “lesson” that helps move the process more reliably towards the projected “probability state”- with repetition, the session theme becomes more naturally available to the user. Brain Engagement also involves a completely integrated audio soundscape interacting dynamically with the light compositional experience. The Brain Engagement soundscape is layered with various styles of brainwave signaling that are woven into a “mood framing” musical background – the “mood framing” element purposely avoids the fully structured characteristics of conventional music, thus avoiding the tendency of the brain to “jump ship” and divert its attention into music and abandon the theme “vector” targeting the neuroplastic change dynamically. Both Brain Enrichment and Brain Priming are methodological sub-sets of Brain Engagement. Like Brain Engagement, each approach is involved explicitly in dynamic neuroplastic change factors.