Accompanied by high ranking officers with swords held rigid at the side, Japanese emperor Michinomiya Hirohito inspects a line-up of Type 90 sound locators on trolleys, in an undisclosed location in Japan, 1930.
Prior to the invention of the radar in 1935, many armies across the world had relied on one or another form of this acoustic device to search out enemy war planes in the dark when look-outs in their observation posts were of little or no assistance at all.
Sound Locators.
A natural evolution of the ear horn that is attested to have been in use as a hearing aid since the 17th century, sound locators had largely come into service during World War I as part of an army’s anti-aircraft arsenal and continued even during World World II – especially in the case of Japan, a nation which at the time had lagged behind the west in technological advancements.
Though different countries had developed these devices as per their own research and specifications, most models had usually comprised of four trumpets attached to two stethoscope like hearing tubes, and had required a team of three or more to operate.
While one person using the hearing tube attached to the first pair of trumpets had gauged the altitude on an incoming plane. The second using the other hearing tube attached to the second pair of trumpets had calculated the distance. This, while the third member, using an instrument attached on the locator itself, had kept track of the direction in which the device was pointing..
Type 90 Sound Locator.
The Japanese Type 90 that Hirohito can be seen inspecting in the photo was developed in the 1930s. Out of the two versions produced at the time, one was of a larger make possibly for use in military bases or cities while the other was smaller in size and meant for field operations.
Like other devices of its kind with other armies, the Type 90 was originally designed to assist anti-aircraft guns on its own.
However, after field tests had revealed their ineffectiveness in accurately pinpointing the location of incoming planes, largely for the amount of calculations required and other factors such as wind velocity, air density and humidity that affects the speed of sound, the Type 90 series were reassigned to assist searchlight crews.
This new role had required them to simply indicate the direction of the an incoming plane for the searchlights to illuminate it and anti-aircraft guns to bring it down.
I F I This is an Independent Story produced to unravel the history behind this featured Vintage Photo taken in 1930, and highlights the role Sound Locators played in pinpointing a war plane’s location at night, before the deployment of radar. It has been created from facts curated from literary and historical sources. I
