Microphones on stage with the orchestra pick up audio signals which are converted into pulses and vibrations of varying intensities by a computer. Different sections of the orchestra are mapped onto different parts of the body (lower strings on the stomach, violins on the chest, brass on the upper back, etc) so that deaf audience members can immerse themselves in classical music just as hearing people can.
Read more at http://www.classicfm.com/discover/music/cute-circuit-sound-shirt/#dMbsB2VqawJQMWOj.99