The evolution of SONAR
From bats to whales, the use of sound waves or ‘echo-location’ has been around in nature for millions of years. The same concept has been used for over 2000 years to understand underwater structures, entities and the sea floor. Listening to underwater sounds was recorded as early as the third century BC, when Aristotle noted that sounds could be heard underwater as well.
A similar observation was made by Leonardo Da Vinci at the turn of 14th century, who noted that a long tube helped hear ships that are a great distance away. Another physicist, Abb´e J. A. Nollet conducted a series of experiments in the 17th century to prove that sound travels faster underwater. The 18th century also saw experiments conducted to measure the speed of sound waves in water by Swiss physicists Colladon and Sturm.
World War I and II
During the First World War, one of the strategies the Germans devised was to use submarines, also known as U-boats, to attack their enemy’s merchant ships.
Launching of a German U-boat during World War II
To detect the presence of submarines, the Allied Forces used a simple underwater listening device similar to a microphone, called a ‘hydrophone’. However this had several limitations – for one, it was a passive device, meaning it could only ‘listen’ for incoming sounds.
ASDIC system. Source: Wikipedia
The research for a more practical system continued and towards the end of the war, a French physicist, named Paul Langevin, assembled an equipment called the ASDIC (Anti-Submarine Detection Investigation Committee), or as it known by its popular name today, the SONAR system. This active underwater acoustic system sent out sound waves and received the resultant ‘echoes’ that were used to pin point the location of the German submarines.
Throughout the Second World War, ASDIC became a commonly used equipment to thwart German submarine attacks by the Allied Forces and the technology proved pivotal.
SONAR in Australia:
After the two wars, SONAR gained popularity for both military and civilian applications. One key industry that saw an uptake of SONAR was Fisheries and Whaling. In Australia, the whaling industry was one of the most profitable industries until whaling operations ceased a few decades ago.
During the early days of commercial whaling in Australia, ships carrying sailors set out every day from the whaling stations. The sailors – with experience – learnt where whales would be, and would throw lines down to bait the whales and use harpoons tied with strong ropes to catch and tow the whales back to the whaling stations.
Cheynes IV Whale Chaser Ship in display at the Albany Whaling Station, WA
The introduction of SONAR made whaling more efficient. SONAR ‘pits’ or cabins were built on ships that had a reading machine, that could be used to send out SONAR signals or ‘pings’ and hear echoes from the whales. Depending on the speed of sound in water, the sailors would calculate the distance and direction of the whale and chase in pursuit of the whale.
SONAR was not just used to locate the whales, they helped the sailors keep track of the whales during the chase, understand whether the whales were heading away or toward the ship and position the ship correctly to catch the whale. While commercial whaling operations have now ceased in Australia, one such SONAR pit can be seen on the Cheynes IV whale chaser ship used by the Cheynes Beach Whaling Company in Albany, WA. The ship is on display at the Historic Whaling Station in Albany.
SONAR in the present day:
SONAR in Australia continues to be used today for various commercial purposes, including mapping the sea floor and for collecting high resolution underwater images.
SONAR model of a current flowing past a wharf
We use SONAR for various applications – to help clients identify the depth of the sea floor, to locate and chart underwater hazards such as wrecks, submerged objects, abandoned wharf piles, trees, etc. We also help clients perform a condition assessment of underwater structures, analyse tides, measure flow speed and direction in the water column and check compliance. Our next blog post will detail how underwater surveying is carried out and how SONAR works. In the meanwhile, if you want to know more about our hydrography services, take a look at our brochure.
Hydrographic Surveyor, Tasmania
Nathan specialises in inshore and coastal hydrographic surveys. He currently works within the technical and business development space of our hydrographic division. Graduating with Honours from the University of Tasmania in computer science. Nathan has used his experience in software development and hardware integration to develop the Veris Hydrographic capability.