What is Brainwave Synchronization?

SmartSound combines a variety of clinical sound techniques and processes including brainwave synchronization and other forms of rhythmic auditory stimulation. Brainwave synchronization provides an excellent example of how sound may be used to modulate neural acitivity for therapeutic effects.

The terms brainwave synchronization, neuroentrainment, auditory driving and brainwave entrainment all refer to a natural phenomenon called 'entrainment'. Entrainment is all about synchronization. An easy way to understand it is to think of dancing, where we synchronize our movements to an external beat or rhythm, or how organisms synchronize to natural rhythms and cycles like day and night.

Brainwave entrainment then, is the synchronization (or partial synchronization) of dominant brainwave patterns to a repetitive external stimulus. This stimulus can be aural as it is in SmartSound, for example by using beats, pulsed tones, clicks or other sounds, (see below), visual, via flashing lights (photic stimulation), or physical, using stimuli like repetitive vibration or movements - or any combinations thereof.

Monaural and Binaural beats, Isochronic tones

As brainwave frequencies occur below the audible range, an audible carrier wave is needed which is modulated with the desired entrainment frequency. Although the carrier frequency is independent of the brainwave frequency itself, studies show some are more effective carriers than others.

There are many ways of modulating sound to facilitate brainwave synchronization including the use of amplitude, frequency, binaural and bilateral modulation. However, the degree of synchronization produced will vary depending on the types and combinations of auditory stimuli used, their modulation, intensity and frequency profiles, the dominant brainwaves and state of the user at the time, and  other factors. Stimulating certain frequencies may also be used to inhibit or decrease the power of others.

The following types of auditory beat stimulation are currently among the most widely used and studied by clinicians, although auditory click stimuli and other forms are also being investigated.

Monaural 'beats' are actual physical beats produced by combining two steady external tones of neighbouring frequency (say 200 Hz and 210 Hz ) to produce a 'beat' (interference pattern) resulting from the difference between the two. In this case it would be 10 Hz, the equivalent of a mid-range alpha frequency. This composite frequency stimulus can be usually delivered to one or both ears simultaneously.

Binaural beats are generated when two neighbouring sine wave frequencies are presented simultaneously but separately to each ear via headphones. Using the example above, this would be 200 Hz in one ear and 210 Hz in the other. But rather than generating a physically perceived external 10 Hz beat using amplitude modulation like monaurals, this process creates the perception (percept) of a 'beat' inside the head resulting from the difference between the two frequencies (frequency modulation).

So, while both ABS methods can be used to encourage brainwave synchronization or entrainment, each engages a different kind of neurophysiological processing. Some researchers consider monaural beats to be 'peripheral' as they are initially detected at the cochlear level (in the inner ear), and binaural beats to be 'central' as they are thought to be processed by the medial superior olivary complex in the brainstem.

Isochronic tones, (wide and narrow) in their simplest form, are evenly spaced beats of a single tone characterised by a rapid onset/offset more akin to a square wave or a 'click'. Studies suggest these, and monaural beats are a far more effective tone-based method for creating brainwave synchronization in certain frequency bands than binaural beats. However, they are less relaxing and pleasant to listen to.

SmartSound includes the above, plus additional and proprietary forms of auditory brainwave synchronization among its techniques and processes.  Why not enjoy a free sample with our 'Mini-D-Stress' session!

NeuroSonica

Hearing is Believing

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