The left earpiece, connected to the blue cable, delivers the NERVANA signal (in addition to the left channel of music when used in music mode). Most people describe feelings ranging anything from tickling to a tingling sensation in the ear canal at the location where the earbud makes contact with skin. You can adjust the intensity of the signal up or down based on your own level of comfort. If the signal in your left ear canal becomes uncomfortable in any way, simply turn the intensity down with the down arrow.
We do not recommend pulling out the left earpiece from your ear when you are in a NERVANA session. If you do pull the left earpiece out while signal is being supplied, then before reinstalling in your left ear, turn down the intensity to a low comfortable level (for example, between 2 and 6).