The modern term Sonar is actually an acronym which stands for Sound Navigation and Ranging. The technique employs sound propagation underwater to navigate, communicate or detect. A sonar can be passive or active. This term, however was not in use universally until about 1960, prior to that sonar devices were called ASDICs. That name came about during WWI and referred to the Anti-Submarine Detection Investigation Committee.¹ Whatever name is used, controversy surrounds who deserves credit for “inventing sonar.”
     Some would start this tale in 1490 with Leonardo Da Vinci. He observed “If you cause your ship to stop, and place the head of a long tube in the water and place the other side of the tube to your ear, you will hear ships at a great distance from you.”² Some would start in 1822. It was then that Jean-Daniel Colloden lowered a bell into Lake Geneva Switzerland. By striking that bell with a hammer and studying the vibrations of a sensor suspended under another boat Colloden calculated, with some accuracy, the speed of sound as it traveled underwater. Four years later Jacques Sturm, a French mathematician, conducted experiments and calculated the speed of sound in water with greater accuracy. His experiments and those of others showed density and elasticity to be important attributes contributing to the speed of sound through water.³
     In 1880, Pierre and Jacques Curie discovered the piezoelectric effect. The decades which followed that discovery saw the development of acoustical detection devices. In 1906 Lewis Nixon, a naval architect, is credited with inventing a passive listening device to detect icebergs.
     Historical events often trigger invention. Reginald Fessenden, a Canadian, whose achievements in radio and broadcasting include the first two-way transatlantic radio transmission in 1906 volunteered his services to the Canadian Government at the start of WWI. Working in London, one of the devices he developed could locate enemy submarines. In 1915 he invented the fathometer for which he won the Scientific American’s Gold Medal in 1929.⁴
     Following the Titanic disaster in 1912, German physicist Alexander Behm researched ways to detect icebergs. His discovery of the technique of echo sounding proved to be a great means of measuring ocean depth. His invention was patented in 1913.⁵ In 1920 Behm bounced sound waves off the bottom of the North Sea and went on to found the Behm Echo Sounding Company.⁶

Trivia: Alexander Behm was also an avid fisherman and developed fishing tackle such as the Behm-fliege and the Behm Blinker.

     With WWI came the need to detect submarines. Fessenden was not the only one in the world working to fill the need. French physicist Paul Langevin, who had been supervised by Pierre Curie in his laboratory classes at the Ecole de Physique et de Chimie Industrielles, was busy at his research;⁷ he is most remembered for work in the field of piezoelectricity.
     Rather than crediting a single inventor for the invention of sonar one begins to understand that many contributed to the technique we call sonar. Through their inquisitive nature, their calculations and their instruments they gave the world a means to “see” where our eyes cannot see.

References

1. “ASDIC AND SONAR SYSTEMS IN THE RCN,” http://jproc.ca/sari/asd_gen.html.
2. “Notable Quotations,” http://www.resonancepub.com/notable_qutoes.htm.
3. “Understanding surveillance technologies: spy devices, their origins & applications By Julie K. Petersen, CRC PressLLC, Chapter 4, pg 417, 2001.
4. “Reginald Fessenden,” NationMaster, http://www.statemaster.com/encyclopedia/Reginald-Fessenden.
5. “Echo Sounding,” Absolute Astronomy.com, http://www.absoluteastronomy.com/topics/Echo_sounding
6. “1900s,” Marine Exploration Logbook, http://­thethunderchild.com/TechnoOcean/Timelash/1900s/1900s.html.
7. “Paul Langevin,” http://www.ob-ultrasound.net/langevin.html.