Yesterday I had a clear illustration of how the brain determines the direction of a noise. I was listening to a podcast in ear buds when my wife asked me something. I took one bud out and talked to her for a while as the podcast continued to chatter in my left ear. Then the cordless phone rang. And I kept spinning around, trying to hear what direction the phone was in, but I couldn’t! You need two ears to pinpoint direction just as you need two eyes for stereoscopic vision.