A delta wave is a high amplitude brain wave with a frequency of oscillation between 0.5–4 hertz. Delta waves, like other brain waves, are recorded with an electroencephalogram and are usually associated with the deep stage 3 of NREM sleep, also known as slow-wave sleep, and aid in characterizing the depth of sleep. The Bedtime Challenge: Go to bed 5 min earlier every week for 12 weeks and feel like a superstar! Follow the #bedtimechallenge playlist: http://phonofile.link/bedtime_challenge Giveaway! Win 150 dollars. How to join: Tag your progress on Instagram by taging a picture of your clock before bedtime with the following hashtags #bedtimechallenge & #asmrsleeptriggers We will pick out two winners at the end of the contest. What kind of sounds do YOU want on the upcoming episodes? Sweet dreams.