You are already far beyond the need for using an entrainment product as a meditation aid. Those who sincerely believe this to be the case would not have come searching for a meditation site such as Project Meditation to help them learn and practice meditation and brainwave entrainment. They would probably not even bother with using an entrainment aid; hence this entire discussion would be irrelevant to them. The fact that you are here, reading this, seeking to benefit from incorporating meditation and brainwave entrainment to aid in your existing meditation practice suggests you are not one of these folks whose development is so advanced that entrainment is of no use to you.
First, go to the restroom and then drink a glass of water so your body won't be a distraction during the process. Choose a quiet spot and make sure no one is going to disturb you for the 30-60 minutes that your chosen track will last for. Get into a comfortable seated position (don't lay down) so that you will be able to stay awake for the whole process.
Another consideration of stress is whether it is acute or chronic. “Acute stress” is what an individual experiences at the time the stressor is encountered (4). The stress response is activated, and the body returns to homeostasis once the challenge of the stressor is removed or the person successfully manages the situation. For example, an individual on the way to an important meeting gets into a traffic jam and realizes she is going to be late; the stress response starts. When she calls her boss and learns that she can conference into the meeting while on the road, the stress response subsides with the resolution of the situation. When an individual experiences acute stress on a consistent basis, such as with overcommitting at work or constant worrying, it is referred to as “acute episodic stress” (4). Individuals who experience acute episodic stress often show signs and symptoms of stress (Table 1) that can negatively impact physical and psychological health. These individuals can learn how to change behaviors and manage their stress to prevent these consequences.
Move-Thru-It Strategy: to support optimum recovery rates, use 6-8 pumps or 3-4 droppers. Repeat every 1-3 hours for a day or two (with a good night's sleep). The idea here is a persistent frequency. Once you have achieved initial results, you can switch to more conventional usage patterns such as 3-4 times a day. For example: Kick-Ass Immune, Get Over It
Women worry more than men do. A study of 166 married couples who kept stress diaries for six weeks found that women feel stress more frequently than men because women tend to worry in a more global way. Whereas a man might fret about something actual and specific—such as the fact that he's just been passed over for a promotion—a woman will tend to worry abstractly about her job, her weight, plus the well-being of every member of her extended family. Keep your anxiety focused on real, immediate issues, and tune out imagined ones or those over which you have zero control, and you'll automatically reduce stress overload.
John Dupuy is the CEO of iAwake Technologies and travels internationally to teach and inspire on the subjects of Integral Recovery, Integral Transformative Practice, and the use of brainwave entrainment technology to deepen one’s meditation practice and in the treatment of addiction, depression, and PTSD. John is the founder of Integral Recovery® and his book Integral Recovery: A Revolutionary Approach to the Treatment of Alcoholism and Addiction  won the 2013 USA Best Book Award. John also hosts interviews with leading innovators in the spiritual technologies field on Spiritual Technologies 2.0 Live and co-hosts the popular Journey of Integral Recovery podcast.
The Delta brainwave is experienced by us every night in dreamless sleep. It is also experienced by advanced yogis and monks who can enter the Delta frequency during deep meditation. This frequency assists in both emotional and physical healing, as well as enhanced immune functioning, significant stress reduction, and even anti-aging benefits. The Delta frequency is a terrific way to experience deep repair on the physical, emotional, and psychological levels.
In physics, entrainment is the process of two oscillating systems coming to assume the same periodic rhythm, such as is observed when two clocks slowly synchronize their ticking and tick together in harmony after some time. Pendulums also achieve this same synchronicity when swinging in close proximity to one another, a phenomenon first observed and written about in 1665 by Christiaan Huygens, a Dutch scientist.

The pitch frequency measures and describes what a beat sounds like, i.e. does the isochronic beat have a deeper bass sound, or is it high pitched and sharper sounding? The beat waveform frequency describes how many times the beat is repeating per second, i.e. how fast it is beating. You don’t really need to concern yourself about the pitch frequency, as that doesn’t have a direct influence on brainwave entrainment and doesn’t play a part on the measurement on an EEG. I only mentioned it because you were referring to humans not being able to hear below 20Hz. I change the pitch frequency just to suit the mood of the track. For tracks that are to be relaxing, for meditation or sleep, I tend to use a lower pitch frequency so it sounds deeper and more relaxing and I never have that lower than 100Hz. For an energizing, high focus track I might use a more higher pitched 200Hz isochronic tone, because that is sharper sounding and less likely to make you feel sleepy. That’s all you really need to know about the pitch frequency.
If mind-consciousness is not the brain, why then does science relate states of consciousness and mental functioning to Brainwave frequencies? And how is it that audio with embedded binaural beats alters brain waves? The first question can be answered in terms of instrumentation. There is no objective way to measure mind or consciousness with an instrument. Mind-consciousness appears to be a field phenomenon which interfaces with the body and the neurological structures of the brain (Hunt, 1995). One cannot measure this field directly with current instrumentation. On the other hand, the electrical potentials of brain waves can be measured and easily quantified. Contemporary science likes things that can be measured and quantified. The problem here lies in oversimplification of the observations. EEG patterns measured on the cortex are the result of electro-neurological activity of the brain. But the brain's electro-neurological activity is not mind-consciousness. EEG measurements then are only an indirect means of assessing the mind-consciousness interface with the neurological structures of the brain. As crude as this may seem, the EEG has been a reliable way for researchers to estimate states of consciousness based on the relative proportions of EEG frequencies. Stated another way, certain EEG patterns have been historically associated with specific states of consciousness. It is reasonable to assume, given the current EEG literature, that if a specific EEG pattern emerges it is probably accompanied by a particular state of consciousness.  

When the track is over you can continue to meditate without the help of the entrainment track.  When you are ready to get up, thank your Higher Self for the experience and remove your blindfold, keeping your eyes closed.  Stay seated with your eyes closed for a few moments, then slowly open them and take a moment to let your eyes adjust to your environment’s light. 
When explaining this to others they frequently respond with something like, “But I had no expectation or even any idea that my face might experience flushing. I didn’t even know that was possible. Now every time I listen to a particular entrainment track that specific face flushing occurs. If it is a specific phenomena, and it only happens when I use one certain entrainment track, doesn’t that prove it is the entrainment causing it?”
Most wisdom traditions have employed methods that allow the subjects' brain waves to slow down such as meditation, [Hindu] kirtan, [Gregorian, Menzuma or Sufi] chanting, Hebrew davening, Native American drum circles and rain chants, Tibetan prayer bowls, and whirling dervishes and African trance dancing. The rhythm of these wisdom tradition technologies actually slows people's brain waves from their normal busy brain frequency we call Beta (13-30 cycles per second or Hz), to Alpha (8-13Hz) -- meditation, Theta (4-8Hz) -- deep relaxation and dreaming, and Delta (.5-4Hz) -- slow wave or dreamless sleep.

Delta (3hz – 0.2hz) – Deep, dreamless sleep. Intuition. Empathy. Brainwave expert Judith Pennington calls it the doorway to Universal Consciousness and “A radar that scans the environment and psychically picks up information and energy.” According to British physicist C. Maxwell Cade “There have been reports that delta waves appear at the onset of paranormal phenomena.” (More information can be found in Cade’s book The Awakened Mind)
People who meditate regularly enjoy many benefits such as increased sense of well being, happiness, contentment, and far less anxiety that many other people. Some believe that this is due to both hemispheres of the brain being in sync with each other, which meditative practice can provide. Therefore, a goal of using technology to entrain the brain and align the frequencies of the brain hemispheres has become a very interesting avenue of science and experimentation.
The use of brainwave entrainment techniques offers many benefits for overall health and well-being, including improved emotional stability, increased cognitive function, and a deepening of creative insight. Much of this benefit derives from the hemispheric synchronization occurring as a result of entrained brainwaves. This effect happens when the electrical impulses in both hemispheres synchronized to the same frequency being delivered through the entrainment source.
Changes in neural oscillations, demonstrable through electroencephalogram (EEG) measurements, are precipitated by listening to music,[20][21][22][23][24][25] which can modulate autonomic arousal ergotropically and trophotropically, increasing and decreasing arousal respectively.[26] Musical auditory stimulation has also been demonstrated to improve immune function, facilitate relaxation, improve mood, and contribute to the alleviation of stress.[27][28][29][30][31][32][27][33] These findings have contributed to the development of neurologic music therapy, which uses music and song as an active and receptive intervention, to contribute to the treatment and management of disorders characterized by impairment to parts of the brain and central nervous system, including stroke, traumatic brain injury, Parkinson's disease, Huntington's disease, cerebral palsy, Alzheimer's disease, and autism.[34][35][36]