The huge problem will all such studies is that there is a clear placebo effect on any kind of mental performance whenever the subject is observed. Do any intervention, then measure performance, and the intervention and measurement are likely to cause an increase in effort and attention which will increase performance. This generic “placebo” effect needs to be factored out of any such study by proper blinding and controls in order for the results to have any meaning at all.
Rudy's primary work is on Alzheimer's. In this disease, beta amyloid proteins form plaques in the brain and kill nerve cells eventually leading to dementia. Research from Washington University School of Medicine in St. Louis shows that when people's brains are in a Delta brain wave state, beta amyloid production in the brain ceases and the toxic material is cleared away. One thought is to explore the possibility of using brain entrainment technology to help treat Alzheimer's, but at this point all it is being used for is to help people meditate, relax and dream instantly and effortlessly.
Other entrainment methods sometimes used include autopan modulation that moves sound in an 180º arc to create a desired tone. Harmonic box entrainment, invented by James Mann, uses a layering of binaural and monaural tones that alternate between ears, requiring headphones. Sound modulation and filtering, amplitude modulation, and pitch panning use diverse sounds to create rhythmic pulses matched to the desired brainwave frequency. 
it says the following: “Running a delta sleep session throughout the night is not recommended as it can interrupt the normal sleep cycle”. I’ve been looping pure delta isochronic tones for about 5 days now, and have had quality sleep. Should I continue looping delta or should I let the videos play out without looping them? Will it will harm my health to do loop delta while I sleep?

A therapy that slows brainwave activity, helping to produce low-frequency waves, is likely to aid relaxation and sleep. But it’s not only lowering brainwave frequency that binaural beats may offer to sleep and relaxation. A small study (19 people) has found that exposure to binaural beats is associated with changes to three hormones important to sleep and well being:
Theta: This brainwave pattern is associated with deep relaxation and with some stages of sleep, including the lighter stages of non-REM (NREM) sleep. REM sleep itself is mostly composed of beta wave and other activity that’s similar to an alert, waking brain. Deep meditation produces theta waves, which are slower and lower frequency (between 5-8 hertz) than Alpha waves. That murky barrier between sleep and wakefulness, when you’re drifting in and out of sleep, and your thoughts feel dreamlike and difficult to remember? That’s a theta-dominant state of consciousness.

Chant in a monotone, enunciating clearly and moving the mouth in a very pronounced way. (exaggerate the lip movements) Pump the navel point with each part of the mantra. (Pull the navel point toward the spine.) Once I have perfected the above I like to add a slight root lock with the pumping of the navel center, which further stimulates the fire in my spine.
While a practical understanding of brainwaves has been around for as long as people have been singing, chanting, and drumming, a scientific view of the electrical activity inside the human brain was not published until 1924 when German psychiatrist Hans Berger developed a machine for sensing and recording activity in the brain by attaching small electrical sensors to the scalp of his patients and recording the resulting electrical activity. Berger’s inventions and discoveries were built upon the earlier work of Richard Caton who published animal studies on brainwave oscillations in 1875.
In the last two posts, I discussed some unusual ways in which some people respond to certain very ordinary sounds. In the case of ASMR, sounds like tapping, tearing, and popping can lead to tingling sensations associated with relaxation and even drowsiness. In the case of misophonia similar sounds, like swallowing and lip-smacking, can also cause a tingling sensation, but one accompanied by disgust and even rage. Binaural beats are a different kind of sound and many people report finding certain of them relaxing and even conducive to falling asleep.  Other people do not like them and after hearing them once never want to hear them again. 
^ Trost W. and Vuilleumier P., Rhythmic entrainment as a mechanism for emotion induction by music: a neurophysiological perspective. In The Emotional Power of Music: Multidisciplinary Perspectives on Musical Arousal, Expression, and Social Control, Cochrane T., Fantini B., and Scherer K. R., (Eds.), Oxford, UK: Oxford University Press; 2013, pp213–225.
Founder and president of Brain Sync, Kelly Howell is internationally acclaimed for her pioneering work in mind expansion. The author of over 60 best-selling audio programs, Kelly is the creator of Brain Sync's Brain Wave Audio Technology. "Kelly Howell is a masterful guide in helping to integrate body, mind, and spirit. In an age where life is becoming increasingly hectic, her instruction is invaluable." Larry Dossey, MD Author: THE EXTRAORDINARY HEALING POWER OF ORDINARY THINGS Eminent scientists and medical professionals such as Harvard-trained neurosurgeon Norman Shealy, MD, PhD have used programs developed by Kelly in their professional practices. Her 20 years of research into spiritual practices and meditation, combined with her work with physicians and biofeedback therapists, have enabled Brain Sync to refine its extraordinary audio technology into the exceptionally powerful, life-enhancing audio programs so many have come to rely on.

Sensorimotor rhythm (SMR) is one final type of brainwave that has been studied. SMR, also known as low beta, is a type of brainwave, which occurs in the sensorimotor cortex, in the 12 to 15 hertz range when that area of the sensorimotor cortex is idle and immobile. The purpose of SMR brainwaves is not well understood, but some neurofeedback practitioners report training to increase SMR brainwaves can be beneficial for people with autism, epilepsy, ADD, insomnia, drug addiction, and as an aide to better manage stress.

There’s an aesthetic element to the music and there are a lot of drone-based sounds and time-stretched sounds, deep, rich bass sounds—there’s a spectrum of sounds within there—and what’s more, there’s a load of 3D processing that goes on to ensure that the mind doesn’t become habituated to them. There’s also a constant, subtle sense, a slow and gradual sense, of the sounds shifting around. And, there are layers of binaural beats.

Theta waves also have been observed in moments when a person recalls information from the past, and this may be what links them also to improvement in learning ability. We also experience theta waves when we go into automatic pilot mode, such as when doing a repetitive task like driving a familiar route where the mind become disconnected while you still drive safely toward your destination.

Besides scientific literature, some authors have written of the promising research on meditation in books targeted for general audiences. One such book, Buddha’s Brain by Rick Hanson, PhD shares the current scientific research and investigations into meditation.[19] Hanson, a neuroscientist and researcher, explains to readers the scientific studies in plain language and discuss the impact of the results. Hanson’s main argument is that positive emotions, like love can be strengthened through meditation in a neuroplastic manner, citing dozens of scientific studies to support this claim.[19] Hanson’s viewpoint is representative of a larger popular movement to study and embrace Eastern phenomena including meditation in the Western world.
Brainwave entrainment also happens with the use of pulsating light, and visual and auditory stimuli are sometimes combined for additional effect and visual stimuli is used alone. Using brainwave entrainment techniques is safe for almost everyone, the exception being pregnant women and people who have seizure disorders who should check with their physician before using these methods.
Effects on cortisol: The hormone cortisol is commonly associated with stress, and when levels are higher than usual, it can have a negative impact on the body. High levels of cortisol can lead to a range of conditions, including Cushing syndrome, menstrual cycle and female libido changes, anxiety, and depression. Dr. Giampapa noted a reduction of cortisol of up to 70-80 percent in several study participants.