Tucker lectured on physics in London. Following the outbreak of World War I, Tucker joined the British Army as a private soldier. He was posted to the Experimental Sound Ranging Station at Kemmel Hill in Belgium which was under the command of Lawrence Bragg. As part of the London Electrical Engineers, Territorial Force, Tucker was granted a commission, being promoted from lance corporal to temporary second lieutenant, General List in April 1916. At Kemmel Hill, Tucker undertook research into 'sound ranging': the process of using microphones and mathematics to determine the position of enemy artillery. Bragg had been wracked by doubts and problems with the military command structure. Tucker formed an experimental sound ranging section, which spearheaded the development of an effective system of sound ranging enemy guns. Vital to the success was Tucker's invention of a 'hot wire' microphone, capable of identifying the shell sound wave and the following report of the gun that fired it. The breakthrough had come from Bragg, who found that the water closet at the farmhouse where he was billeted, allowed him, once seated inside, to detect sound and pressure differences of shell waves and gun waves as they passed overhead. Tucker researched how to cool platinum wire with the air currents caused by the sound-waves they were detecting. Mouse-holes and rum jars provided a clue here, as there were two mouse-holes by Tucker's bed and he noticed a draught of cool air whenever the gun-wave arrived. Tucker devised a microphone consisting of a thin, electrically heated wire, stretched over a small hole in a container. The decrease in the electrical resistance of the wire as the gun-wave struck was recorded by a Wheatstone bridge and galvanometer. Tucker had to send for platinum wire to be delivered to him at Kemmel Hill, before he could run trials. The rapid oscillations of the shell waves had almost no effect on the wire, whilst the gun-reports resulted in well-defined 'breaks' on the 35mm cine film used to record the oscillations, due to the deflection of the wire by the pressure of the gun wave. By September 1916, Tucker's new microphones had been supplied to all sound-ranging sections. In 1917, sound-ranging was further developed so that allowances could be made for poor weather conditions, as sudden gusts of wind could cool the wire: the most effective method found was to wrap the devices in several layers of camouflage netting. Tucker developed a system of moveable microphones to improve detection techniques, allowing for a high degree of accuracy in determining the position of the enemy guns. By the end of the war it was possible to determine where the gun was pointing, and how large it was. The technique could also be extended to listen out for enemy aircraft; as a result, Tucker became Director of Acoustical Research, Air Defence Experimental Establishment, Biggin Hill. His work eventually led to vast parabolic 'sound mirrors' being constructed from concrete. Some of these sound mirrors still survive along England's south coast, such as those to be found at Denge, near Dungeness, to the west side of a lake slightly north of Lydd-on-Sea, and others uncovered in 2014 at Fan Bay near Dover. Tucker's work was superseded by the development of radar, which made sound-ranging using the great concrete mirrors obsolete. Some known locations for the sound mirrors were documented in a series of photographs by Joe Pettet-Smith in 2018.
