In 1963, Harvard Medical School Professor David Littmann, a renowned cardiologist, invented a stethoscope which would revolutionize the world of medical auscultation. Stethoscope design had changed little since the nineteenth century but Littmann realised that the requirements for listening to low and high pitch sounds were different. Accordingly he patented his dual sided stethoscope which incorporated a chest piece with an open side for listening to low pitch sounds and a closed side which filtered out lower pitched sounds. In addition, the Littmann stethoscope incorporated features which made it comfortable for the practitioner to use as well as light and practical to carry. The level of sound produced by the new design made such a profound improvement on what had gone before that in 1967 the 3M corporation acquired Dr Littmann