Theta waves have another interesting characteristic. The Earth has a measurable resonance of 7.83 hertz known as the Schumann resonance. Because the Schumann resonance is a constant background frequency surrounding all life, it may play a special role in biological activity. The Schumann resonance frequency falls within the range of theta brainwaves and may have something to do with why these brainwave frequencies are so powerful. 
... One of the possible explanation for insignificant results could be length of exposure to AVS. Our participants were exposed to it for 11 minutes, while some authors (Cruceanu & Rotarescu, 2013) suggest that at least 20 minutes is needed for the positive effects to take place. Furthermore, part of our reserach was also visualization of gymnastic skills, performed after AVS. ...
By exposing an individual to repeatedly external stimulus which can be flashing lights and/or recurring sounds, the entrainment process consists in pushing the brain to adjust to match the frequency provided. Unlike other forms of neurotherapy which require the individual to actively respond to stimulus, entrainment creates an immediate neurophysical response which is instinctive and effortless for the person being provided with the light and/or sound combinations. The key outcome of the sensory stimulation is known as the ‘Frequency Following Response’.
Theta brainwaves occur most often in sleep but are also dominant in deep meditation. Theta is our gateway to learning, memory, and intuition. In theta, our senses are withdrawn from the external world and focused on signals originating from within. It is that twilight state which we normally only experience fleetingly as we wake or drift off to sleep. In theta we are in a dream; vivid imagery, intuition and information beyond our normal conscious awareness. It’s where we hold our ‘stuff’, our fears, troubled history, and nightmares.
There are many ways to reduce tension and relax, but some are more effective than others. Some techniques are difficult to learn while others are challenging to practice. Others have negative consequences that almost outweigh their effectiveness or can create bigger problems. Here are ten stress relievers proven to be among the most effective for the amount of work and time involved. Most can be learned in the time it takes to read this page and will help you to feel more relaxed almost immediately. And even more exciting, the ​stress relief benefits will increase with regular practice. Try as many as you can—there's something here for everyone.
♥ Imagine a really bad ringing in your ear and the pain that it brought along or when your ear was throbbing with pain. Can you remember the sound coming from that ear? Probably not, since the pain was probably far more memorable. This sounds very similar to that, but it is not at all painful. Quite a unique experience, really. Try it out, but you need to be wearing earphones and have the volume up.
The functional role of neural oscillations is still not fully understood;[6] however they have been shown to correlate with emotional responses, motor control, and a number of cognitive functions including information transfer, perception, and memory.[7][8][9] Specifically, neural oscillations, in particular theta activity, are extensively linked to memory function, and coupling between theta and gamma activity is considered to be vital for memory functions, including episodic memory.[10][11][12]