Theta waves have a frequency between 4 and 7.5 hertz, making them slower than more wakeful alpha but faster than the dreamless slumber of delta. Theta brainwaves are the frequencies of nighttime dreams and REM sleep when the brain goes through bursts of activity and eye movement. People also experience theta waves in a state of light sleep, deep relaxation, during meditation and prayer, and when daydreaming. Theta waves produce an experience of inward wakefulness where we become disengaged from the outside world while engaging in inner activity. At the lower frequencies of theta, sleeping states are experienced, and at the higher range of frequency, awake relaxed states are experienced. 
Entrainment is a phenomenon seen is a wide variety of different natural circumstance. In the field of chronobiology, the study of biological rhythms in living organisms, entrainment is the synchronization of a circadian rhythm with the rhythm of an external pattern, such as the synchronizing of women’s menstrual cycles with the phases of the moon or with one another in a group.
All of this is entirely understandable, even somewhat predictable. Unfortunately, it quickly becomes counter-productive. Such experiences, while having a certain feeling of solidity to them, are largely the product of our desires and expectations. Did your face get flushed? One look in the mirror confirms it did. Was this caused by the entrainment? No, it was not. It was the result of what was sought after and what was expected or even hoped for.

For example, according to Wikipedia, if you take one frequency in one speaker in a pair of headphones, say, 300Hz, and the other speaker for your other ear has a frequency of 310Hz, the resulting difference of 10Hz would be the rate that the pulse, or beat, plays at. 10Hz (Alpha Waves) would correspond to what the brain puts out when you are generally relaxed. So, in effect, listening to a 10Hz binaural beat for a certain amount of time should take the edge off.
Stress levels and a proper diet are closely related. When we’re overwhelmed, we often forget to eat well and resort to using sugary, fatty snack foods as a pick-me-up. Try to avoid sugary snacks and plan ahead. Fruits and vegetables are always good, and fish with high levels of omega-3 fatty acids have been shown to reduce the symptoms of stress. A tuna sandwich really is brain food.
With its focus on full, cleansing breaths, deep breathing is a simple yet powerful relaxation technique. It’s easy to learn, can be practiced almost anywhere, and provides a quick way to get your stress levels in check. Deep breathing is the cornerstone of many other relaxation practices, too, and can be combined with other relaxing elements such as aromatherapy and music. While apps and audio downloads can guide you through the process, all you really need is a few minutes and a place to stretch out.
Research shows that listening to soothing music can lower blood pressure, heart rate, and anxiety. “Create a playlist of songs or nature sounds (the ocean, a bubbling brook, birds chirping), and allow your mind to focus on the different melodies, instruments, or singers in the piece,” Benninger says. You also can blow off steam by rocking out to more upbeat tunes -- or singing at the top of your lungs!
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]