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.
Cortisol is the principle hormone (although not the only hormone) tied to our innate “flight-or-fight” response, which is how the body reacts to acute stress by either helping us run from the situation or stick around and fight our way through. When short spikes in cortisol/adrenaline happen over and over again nearly every day, they cause wear and tear on the body and speed up the aging process.

So, in summary, binaural beats certainly do not work the way the sellers claim, but there's no reason to think they're any less effective than any other music track you might listen to that effects you in a way you like. If they make you sleepy (like they all do for me), use them to go to sleep. If they relax you or get you amped, use them for that. But don't expect them to be any more effective than regular music. If someone you know claims that they are, put them to the test, and bust the myth.
Music therapy has shown numerous health benefits for people with conditions ranging from mild (like stress) to severe (like cancer). When dealing with stress, the right music can actually lower your ​​​blood pressure, relax your body and calm your mind. Here are some suggestions of different types of music to listen to, and how to use music in your daily life for effective stress management.
Summaries from recent reviews on yoga or Tai Chi clinical trial interventions indicate that these mind-body types of exercise can be effective in reducing stress (7,14,17). The authors of these reviews suggest that the results should be viewed with caution because study quality was varied (7,17). However, it should be noted that reductions in stress reported in one review were similar to or greater than reductions from other types of commonly used stress management techniques (7).
Stress can either be perceived as feeling good/positive or bad/negative depending on the context, and the body reacts differently to both kinds. However, where the body isn’t so clever is distinguishing between very serious threats (like being robbed or starved) and events that are stressful but not actually life-threatening. Unfortunately, whether a problem is very serious or not, the body usually has no way of knowing the difference− — anything that causes you to worry, anticipate, regret, overthink or panic can send your stress levels through the roof.
Physical activity can pump up your feel-good endorphins and other natural neural chemicals that enhance your sense of well-being. Exercise can also refocus your mind on your body's movements, which can improve your mood and help the day's irritations fade away. Consider walking, jogging, gardening, housecleaning, biking, swimming, weightlifting or anything else that gets you active.
Entrainment is a term originally derived from complex systems theory, and denotes the way that two or more independent, autonomous oscillators with differing rhythms or frequencies, when situated in a context and at a proximity where they can interact for long enough, influence each other mutually, to a degree dependent on coupling force, such that they adjust until both oscillate with the same frequency. Examples include the mechanical entrainment or cyclic synchronization of two electric clothes dryers placed in close proximity, and the biological entrainment evident in the synchronized illumination of fireflies.[13]