Best answer by jat0rz
The double lines is simply a visual representation of how many audio channels your device has.
Are you saying you can actually hear your audio being doubled? If that is the case:
Echoes usually occur when there is a monitor set in the mixer, ensure they are all set to MONITOR OFF http://prntscr.com/kfl5m7
They can also occur due to custom audio devices set in your video capture device, ensure you have none selected: http://prntscr.com/kfl60h
If none of these resolve the issue, it could also be that you have your stream open (unmuted) in another browser window;
Or that you're listening to a recording device from within windows. Be sure to mute the stream and turn off this option: http://prntscr.com/kfl6ct