Since ancient times, different cultures and traditions have used sound in practices intended to alter the emotional and physical state of the person. Examples of this are Tibetan chants, Gregorian chants, the use of the drum in shamanic traditions and mantras in meditation.
Currently, in the context of our scientific method, the study of the perception of sounds and their impact on our psyche is indicated with the term psychoacoustics.
One of the phenomena studied by psychoacoustics is the ability of our brain to "sync" with the frequency of external stimuli. What is synchronized in this process is the frequency of the brain waves or, in other words, the frequency at which the neurons communicate with each other.
The frequency of brain waves can be measured with a electroencephalogram (EEG), a technique that measures the electrical activity of our nervous system using electrodes positioned on the scalp.
Our brain waves vary depending on what we do and feel. When lower frequencies are dominant, we feel tired, sluggish, or dreamy. When high frequencies predominate we are more active and alert.
Brain frequencies are divided into categories according to their function and are measured in Hertz (cycles per second):
INFRA-LOW WAVES (< 0.5 HZ)
The lowest in frequency and for this reason the most difficult to study and measure. Very little is known about this category of waves. They seem to play a fundamental role in the synchronization process of our nervous system.
DELTA WAVES (0.5 to 4 Hz)
Delta waves can be found in deep sleep phases and in the deeper stages of meditation. Delta waves characterize the suspension of the perception of the external world, favor healing and regeneration. In fact, a deep restorative sleep is often associated with rehabilitative processes.
ONDE THETA (da 4 a 8 Hz)
Theta waves are generally associated with sleep and meditation. In this phase we interact with our inner world made of dreams, visions, memories and intuitions. Theta waves demarcate the territory within which we keep our fears and forge our imaginary world. Daydreaming and creative activities are associated with this type of brainwave.
ALPHA WAVES (8 to 12 Hz)
Alpha waves reflect the quiet state of the mind. These brain waves are predominant during the normal flow of thoughts and in some light states of meditation.
BETA WAVES (13 to 30 Hz)
Beta waves are dominant in the normal waking state, during which our attention is directed towards the outside world in a state of alert. When we focus on a problem, make judgments or decisions we are in the Beta phase.
GAMMA WAVES (30 to 70Hz)
Gamma waves are the fastest of the diagnosed brain waves and denote information traffic that simultaneously affects different areas of the brain. The speed of Gamma frequencies is higher than the speed of neuronal processes, which leaves a mystery as to what these waves are generated by. For a long time, Gamma waves were considered simple brain "noise" until their presence was regularly found in some states of mind, in particular when the mind is focused on concepts such as altruism and universal love, or other dispositions of mind that foresee an expansion of consciousness towards totality.
Brain Synchronization (BrainWave Entrainment)
Just like our heartbeat and breathing, the rhythm of our nervous system is also indicative of our emotional state and mental disposition. From the activities carried out at a cellular level to the functioning of our organs, we are a complex mix of rhythms, destined to constitute a harmonious state of health, or a noisy state of imbalance when we break the harmony between the parts. Different cause and effect patterns can be drawn between one rhythm and another, but in fact everything works holistically. Each part of the whole is influenced by and influences the other parts.
Brain synchronization, or neural synchronization (in English “Brainwave entrainment”, or BWE) uses rhythmic stimuli to alter brain frequencies and consequently the state of mind. Using rhythmic stimuli, the brain is induced to synchronize its dominant frequency to the rhythm of the chosen pulse.
The stimuli used are generally visual or acoustic. In the first case, light pulses are projected onto the patient's eyes (usually closed), at the desired frequency. However, in the case of acoustic impulses, some characteristics of the sound are exploited, including the phase, frequency and amplitude of the sound wave, to bring the brain waves to the desired frequency.
The 3 most common forms of acoustic stimulation are isochronic tones, binaural beats and monaural beats.
Monaural beats
The beat is the frequency resulting from the superposition of two waves (usually sinusoidal) having different frequencies that are close to each other.
For example, if we superimpose a sound wave of 200 Hz on another sound wave of 205 Hz, we obtain a third sound frequency (a beat) equal to the difference between the two initial waves (in this case 205-200 = 5 Hz).
This phenomenon can be experienced by vibrating two tuning forks next to each other or when tuning musical instruments.
The beat effect becomes less and less perceptible as the difference between the two frequencies increases. Typically, if the difference between the two frequencies exceeds 30Hz, the beat becomes imperceptible and we instead begin to hear the two frequencies as two separate voices.
This category of beats is called monaural because a single sound diffusion channel is sufficient to reproduce the beat effect. The monaural beat is perceptible even with a single ear, unlike binaural beats.
Binaural beats
Binaural beats are generated by playing two tones of slightly different frequencies in each ear.
The binaural beat requires the use of two distinct sound diffusion channels and both of our ears to be perceived. For this reason, the use of headphones (preferably circumaural, i.e. covering the entire ear) is recommended, in order to receive the impulse cleanly and correctly.
Binaural beats are generated directly by the brain which superimposes the two frequencies, detects the phase difference between the two sound waves and obtains a third frequency equal to the difference between the two. So if we listen to a 347.5 Hz tone with the left ear and a 340Hz tone with the right ear, we will hear a third frequency of 7.5 Hz, entirely generated by ourselves.
As in the case of monaural beats, the more the difference between the two frequencies increases, the less distinguishable the beat is, until the effect disappears when the difference exceeds more or less 30Hz.
Isochronic tones
Isochronic tones are pulsed tones, that is, they are interrupted by equally spaced pauses of silence, which are repeated at the desired frequency. Unlike binaural beats and monaural beats, where the overlapping of frequencies creates a soft pulsation, in isochronic tones it is the amplitude (the volume so to speak) that is rapidly modulated, so as to create pulsations that are clearly distinguishable from each other, thanks to the clear silence between one pulse and the next.
Care of mind and body
The first known clinical use of neural synchronization is attributed to the French psychologist Pierre Janet. At the end of the 1800s Janet noticed a decrease in depression, tension and hysteria in her patients when they were asked to fix their gaze on a rotating disk with holes, behind which a lit lantern was positioned. The light, through the rotating disk, created a stroboscopic effect, responsible for the change noticed in the patients. From Janet onwards there has been a series of studies on the effects of optical impulses, followed by experiments conducted with other types of impulses (tactile and sound) and by a large series of tests comparing rhythmic stimulation with the emotional condition of the patient. 'individual.
Lo sviluppo di metodi per la sincronizzazione cerebrale iniziò a proliferare dopo l’articolo del biofisico Gerald Oster del 1973. Nel suo articolo Oster descrive l’effetto dei battimenti binaurali (binaural beats) and suggests their use in studies on perception.
Research conducted in the field of Neuronal Synchronization has associated brain waves with all sorts of emotional and neurological conditions. Every change in our perception results in a change in brain waves. Excessive activity on some frequency bands is linked to states of depression, anxiety, insomnia, nightmares, aggression, anger. Below normal activity on some brain frequencies is linked to attention deficit, insomnia problems, chronic pain.
Neural synchronization is used to induce different states of consciousness including: trance, meditation, cognitive attention, relaxation, sleep.
Warning
Although the frequency bands (delta, alpha, beta etc..) are useful for locating the area of interest on which one wants to work, they provide a rather simplistic picture of the real situation. Our brain never operates at a single frequency, but rather is an intertwining of different frequencies which, like a symphony, forms our current state of psycho-physical health. There are predominant frequencies depending on the activity carried out and the mental state one has at a given moment, but there is always the presence of multiple frequencies operating simultaneously. So you can, for example, be in the REM sleep phase and have alpha frequencies active, albeit to a minimal extent compared to theta frequencies.
Going to work on brain waves is for many a shortcut to access some states of consciousness that are otherwise difficult to reach without long discipline, such as yoga or meditation. Also for this reason neural synchronization is becoming increasingly known.
Obviously, work of this type also presents risks. For example, in 1997 a Japanese television broadcast a cartoon that contained 5 seconds of flashing lights. The episode caused epileptic seizures in hundreds of children who were watching the cartoon (according to a national survey at least 618 children suffered convulsions and vomiting after watching the cartoon). If an individual suffering from epilepsy is exposed to a stimulus with the same frequency as that experienced during attacks, he or she will go into an epileptic seizure. Each person is different, with their own needs and particularities, which makes it impossible to have the same recipe or treatment for everyone.
Those who want to rely on tools developed by science to understand if and which type of neural synchronization is right for them can make use of analysis tools such as EEG (electroencephalogram) and the QEEG (quantitative electroencephalogram). Another interesting tool is a particular type of diagnosis called neurofeedback. Neurofeedback consists of monitoring neurological alterations in order to stimulate the patient's ability to voluntarily self-control processes previously considered involuntary.
Tools of this kind, together with techniques such as neuronal synchronization, are part of the relatively recent trend that goes by the name of bio-hacking.
Personally I find the tendency to want to "hack" one's body and mind inspiring. This approach raises the question "who hacks what?", bringing the question to a metaphysical level, where human beings try to escape their limits by experimenting.
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