Underwater acoustics (1938 – 1945)
On April 5, 1938, the Commission for Physical Armorment received a (very secret) assignment from the Dutch Department of Defence for research in underwater acoustics with the periphone and for studying the problem of noise reception under water. The underwater acoustic experiments took place in the Kanaal door Voorne, in the Westeinderplas (Aalsmeer), and at sea on board Hr. Ms. M2 (Minesweeper).
The periphones developed by the laboratory consisted of magnetostrictive plates of nickel and Monel. They were successfully compared with a periphone from Atlas Werke A.G. affixed to the Dutch submarine O-16.
At the outbreak of the German occupation in May 1940, the underwater acoustics research was discontinued for obvious reasons. However, during the entire war period research into magnetostrictive materials continued. These materials could be important for the Dutch PTT as well. This research laid a good foundation for the transducer developments after World War II.