Underwater acoustics (1946 – 1948)
During the Second World War, underwater acoustics found application in the search for submarines and surface vessels on a fairly large scale. The systems used for this purpose were first called ASDIC after the Anti-Submarine Detection Investigation Committee. The later name was sonar (Sound Navigation and Ranging). The systems could be “active” or “passive” types. Active sonar is based on receiving an echo from an object after the transmission of a signal (“ping”). The passive method uses the detection of the sound produced by an object such as ship propulsion.
In 1946, the Netherlands made reluctantly restarted its fundamental underwater acoustics research. The first research concerned noise absorption in liquids. At the same time, work started on the development of a streamlined sonar dome that generated less cavitation, or in other words sound, in collaboration with the Dutch Shipbuilding Testing Facility, the later MARIN.
In 1947, the Royal Netherlands Navy commissioned the investigation of an extensive sonar installation that was present in a left-behind German warship and the repair of the American sonar system aboard the HNLMS Queen Wilhelmina patrol vessel (former USS PC 468 and temporarily the Royal Netherlands Navy Auxiliary ship Experimental (HE 1) between 15 June and 15 July 1949).
At the end of 1947, the Royal Netherlands Navy expressed the opinion that, given the future importance of sonar, the development of ASDIC expertise and experience within the Netherlands was a necessity. In 1948, the laboratory was tasked to develop a sonar for the new Navy shipbuilding program. Neither the Brits nor the Americans were willing to provide any information about sonar technology. France was in a similar position. Therefore, both nations started extensive research cooperation activities. This concerned the joint development of transducers and hydrophones (=underwater microphones) as well as the exchange of experience with equipment under development. France also provided sonar test facilities to the Netherlands.