text: During World War I, Rutherford worked on a top-secret project to solve the practical problems of submarine detection. Both Rutherford and Paul Langevin suggested the use of piezoelectricity, and Rutherford successfully developed a device which measured its output. The use of piezoelectricity then became essential to the development of ultrasound as it is known today. The claim that Rutherford developed sonar, however, is a misconception, as subaquatic detection technologies utilise Langevin's transducer.