I want all of you to look at the image and perform your very best Arnold Schwarzenegger voice saying: "It's not a tuba!"
So what exactly is the Japanese War Tuba? Known as the Type 90 Large Detector (see large or regular-sized version above - that's Japan Emperor Hirohito on the left), it is a military listening device akin to sonar or echo location, but really, it is an acoustic location device that was used by global military organizations from the middle of WWI through into the very early days of WWII.
Basically, it was used to listen for the approach of enemy aircraft by the noise of their engines.
Please note that the Japanese did NOT invent this concept.
Now, most of us are far too young to have actually seen anyone use an ear trumpet, that helped amplify sound for people hard of hearing—yes, this was before hearing-aids made life a lot more convenient for a lot of people. But basically, the Japanese War Tuba is like an ear trumpet.
Each locator consists of two pairs of horn detectors, one pair on a horizontal axis and one pair on a vertical axis. The output of each pair is attached by rubber hoses to a stethoscope-type headphone worn by a technician.
By using their stereophonic hearing and rotating the horn axis until the aircraft noise sounds "centered" in the earphones, the bearing and elevation of the aircraft can be determined.
And despite the complex nature of the equipment, it still looks like the end result after a brother tuba marries a sister tuba.
|A smaller version of the Japanese Type 90 Small Detector. circa 1932 - Oom-pa-pa!|
The acoustic locators were rendered obsolete by the invention of radar. The word 'radar', by the way, was actually all caps as RADAR, and was an acronym for RAdio Detection And Ranging—as described by the U.S. Navy in 1940.