Neural oscillations are rhythmic or repetitive electrochemical activity in the brain and central nervous system. Such oscillations can be characterized by their frequency, amplitude and phase. Neural tissue can generate oscillatory activity driven by mechanisms within individual neurons, as well as by interactions between them. They may also adjust frequency to synchronize with the periodic vibration of external acoustic or visual stimuli.[3]
Consider the following analogy. Imagine a ballroom full of people dancing together. When the music changes to a faster tempo, the dancers move faster in response to this. When a slower piece of music is played, the dancers’ rhythm slows down as well. In a similar way, the frequency of your brain will change in response to the frequency of the binaural beat that it is exposed to. For example, a person who is in a state of very deep meditation may have a dominant brainwave frequency of 5 hertz, so by listening to a binaural beat with a frequency of 5 hertz you can entrain your own brainwaves to a similar state.
Many people experienced in using alpha brainwave entrainment report that the state of mind associated with alpha waves is a time when they feel most consciously connected to their subconscious mind. The intense experience of hypnagogic sleep, reported by some people as a feeling of being awake and asleep at the same time, is also associated with alpha brainwaves.
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.

Subsequently, the term 'entrainment' has been used to describe a shared tendency of many physical and biological systems to synchronize their periodicity and rhythm through interaction. This tendency has been identified as specifically pertinent to the study of sound and music generally, and acoustic rhythms specifically. The most ubiquitous and familiar examples of neuromotor entrainment to acoustic stimuli is observable in spontaneous foot or finger tapping to the rhythmic beat of a song.

Hi Rona, thanks for your compliments on my videos and the music I use, I’m pleased you’ve found them helpful. Regarding the pulse-like sound you’ve been hearing, I’ve never had anyone report something similar to that before. I also haven’t heard anyone on brainwave entrainment forums mention it. That is very unusual and because I’ve never come across it before, I’m afraid I don’t know what would cause that.
For a little variety, you can use the 60 minute Delta Ultra Deep Standalone Meditation which takes you down into Delta and holds you there for an extended period of time. If you can stay awake during this entire time, you will have some amazing meditative experiences. (If you fall asleep, don't worry! It's natural and with practice you will be able to stay awake more often.)
Synchronized brain waves have long been associated with meditative and hypnogogic states, and audio with embedded binaural beats has the ability to induce and improve such states of consciousness. The reason for this is physiological. Each ear is "hardwired" (so to speak) to both hemispheres of the brain (Rosenzweig, 1961). Each hemisphere has its own olivary nucleus (sound-processing center) which receives signals from each ear. In keeping with this physiological structure, when a binaural beat is perceived there are actually two standing waves of equal amplitude and frequency present, one in each hemisphere. So, there are two separate standing waves entraining portions of each hemisphere to the same frequency. The binaural beats appear to contribute to the hemispheric synchronization evidenced in meditative and hypnogogic states of consciousness. Brain function is also enhanced through the increase of cross-collosal communication between the left and right hemispheres of the brain.
The most common way to use a brainwave entrainment is for a short-term benefit, to help guide your brain into a particular mental state at the time you need it.  In a similar way to how you might take a sleeping pill before bed to help you get to sleep, or maybe drink some coffee or an energy drink to help wake you up and give you a boost of energy.
I am very encouraged by my stroke recovery progress after starting with Sacred Acoustics! I have been listening to the extended Light Body (non verbal) recording almost constantly. I keep it on the repeat mode and at a low enough volume so that I do fine with ordinary conversation as I go about my daily activity. The results with constant listening of Light Body are so fantastic, I hate to stop! 
It might surprise you to learn that biological stress is a fairly recent discovery. It wasn't until the late 1950s that endocrinologist Hans Selye first identified and documented stress. Symptoms of stress existed long before Selye, but his discoveries led to new research that has helped millions cope with stress. We’ve compiled a list of the top 10 ways to relieve stress.
At Gaia Meditation, most of audio programs including free relaxation music, free sleep music, free meditation music etc. use the technology of brainwave entrainment (or “brainwave synchronization”) with powerful binaural beats and isochronic tones. Our audio tracks utilize pure and precisely tuned sound frequencies which will drive your brain activity (consciousness) into your desired state: Gamma, Beta, Alpha, Theta or Delta.
♥  I'm an ADHD high school student and I've found that this sound really helps me to get my homework done. Normally, I would be up very late writing essays and studying for tests because I can't sit down and focus on them, but this helps me to focus and also keeps me awake even late at night so I can continue to work. I love this site and I know I'll use it for a long time!
^ 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.