Ever had the strange tingly feeling in the back of your head? something that you just can't explain? Well, in recent years it has been given a name. A.S.M.R, this stands for Audio Stimulatory Meridian Response. The sensation is triggered by good or bad associations with sounds. Often people refer to the good version of this phenomenon as a "headgasm". In recent times a community has developed on YouTube dedicated to inducing a positive ASMR response. These videos added together have almost a billion view. Often times people will seek to have an ASMR experience in order to fall asleep at night. Dartmouth University is currently conducting and ASMR study in order to find the medical root of this feeling. But one explanation for this feeling is that it is a rush of dopamine to the brain causing a euphoric feeling.
Here is a link to one of my favorite ASMR YouTube channles:The Water Whispers Ilse 
Also here is a link to the Reddit community for ASMR: Reddit