Using the Booster
You can enable the Booster under the Settings tab, and you can adjust its volume on the main Listen screen. Because binaural beats deliver a different sound frequency to each ear, you must use headphones or earbuds to experience the benefit. When the Booster is enabled, you'll hear a gentle hum. Set the volume so the hum is just barely audible. A higher volume does not increase its effect, and you may find the higher volume distracting. It's perfectly fine to listen to the Booster along with the background music or nature sounds.
About the Premium Features