April 16 is World Voice Day, a day to celebrate the phenomenon of the human voice, and to remind us of the enormous importance of the voice in our daily lives. Not only is the voice a tool of communication, it is used as an application of a large number of sciences, such as physics, psychology, phonetics art and biology. We talk with Dr. Steven Sims, Director of the Chicago Institute for Voice Care, about the science behind the voice and what we continue to learn about it. (Photo: Flickr/alphadesigner)