Cymatics is the study of a modal vibrational phenomena. The name was coined by a Swiss follower of the philosophical school known as anthroposophy named Hans Jenny. Usually the surface of a plate or membrane is vibrated, with the areas of displacement being made visible by a thin coating of particles or a liquid such as sand or water.
According to Cymascope.com, the CymaScope is a new type of scientific instrument that makes sound visible. They even have a CymaScope app.