Underwater acoustics (1938 – 1940)
On 5 April 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 transducer consisted of magnetostrictive blocks of nickel. The underwater sound experiments took place in the Kanaal door Voorne, in the Westeinderplas (Aalsmeer), and at sea on board Hr. Ms. Mijnenveger M2 (Minesweeper). At the outbreak of the war in May 1940, the research was discontinued for obvious reasons.