First and foremost, headphones or earbuds are a great way to help you tune out the external world of noise and stress and focus solely on your meditation or introspection. Additionally, some audio brain entrainment can be of benefit only if both ears are engaged with different frequencies. So, we put one frequency in the left headphone and another in the right headphone. As you play the audio through headphones, each ear receives only its frequency, and not the frequency the other ear receives, thereby creating the entrainment process.