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. 
How does brainwave entrainment work? Consistent, precisely engineered audio frequencies in the form of binaural beats cause the brain’s frequencies to match the stimulus. Your brain perceives two beats with slightly different frequencies (which are inaudible to the ear) through your headphones. It takes the difference between the two, and matches its own frequency to it. This is called the “frequency following” response.
There has been considerable interest in the potential of auditory beat stimulation to affect cognition and mood states.  Chaieb, Wilpert, Reber, & Fell (2015) reviewed the literature on the effects of auditory beat stimulation on memory, creativity, attention, anxiety, mood, and vigilance. They found some support for it being able to affect these modalities but there were contradictory findings. So the area clearly requires significantly more research before firm conclusions can be drawn. 

Well, except for one reason: The power of suggestion. If I give you a music track and tell you that it will cure your headache, you're more likely to report that it cured your headache than you are to say "Well it didn't effect my headache, but it made my short-term memory better." An interesting experiment would be to buy a binaural track claimed to induce drunkenness, for example; play it for five friends without telling them the claim, and then ask how it made each of them feel. Give them multiple choices to select from. Chances are they're going to respond all over the map. If you have a friend who is a believer in binaural beats, I suggest going ahead and setting up this little test.

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.