DidJaKnow? Large WWII Ears Were Developed

Do not go where the path may lead, go instead where there is no path and leave a trail.

Acoustic Location Devices During WWII

Acoustic location is the art and science of using sound to determine the distance and direction of something. Location can be done actively or passively, and can take place in gases (such as the atmosphere), liquids (such as water), and in solids (such as in the earth).

Acoustic location in air was used from mid-World War I to the early years of World War II for the passive detection of aircraft by picking up the noise of the engines. It was rendered obsolete before and during World War II by the introduction of radar, which was far more effective. Acoustics has the advantage that it can see around corners and over hills.

Did you know? - Prior to World War II and the invention of radar, acoustic mirrors were built as early warning devices around the coasts of Great Britain, with the aim of detecting airborne invasions. The most famous of these devices still stand at Denge on the Dungeness peninsula and at Hythe in Kent. Other examples exist in other parts of Britain (including Sunderland, Redcar, Boulby, Kilnsea) and Selsey Bill, and Bahar ic-Caghaq in Malta. The Maltese sound mirror is known locally as "the ear" (il-Widna) and appears to be the only sound mirror built outside Great Britain.

Acoustic mirrors
These were quite inexpensive to construct in the 1930's

In 1934 a large-scale Air Defense exercise was held to test the defenses of Great Britain and mock raids were carried out on London. Even though the routes and targets were known in advance, well over half the bombers reached their targets without opposition. Prime Minister Baldwin's statement "The bomber will always get through" seemed true.

To give time for their guns to engage enemy aircraft as they came over, the Army was experimenting with the sound detection of aircraft by using massive concrete acoustic mirrors with microphones at their focal points

The Dungeness mirrors, known colloquially as the "listening ears", consist of three large concrete reflectors built in the 1920s–1930s. Their experimental nature can be discerned by the different shapes of each of the three reflectors: one is a long, curved wall about 5 m high by 70 m long, while the other two are dish-shaped constructions approximately 4–5 m in diameter. Microphones placed at the foci of the reflectors enabled a listener to detect the sound of aircraft far out over the English Channel. The reflectors are not parabolic as sometimes imagined, but are in fact hemispherical mirrors. This design element is their genius, because in addition to being able to detect range (over 30 km, or 20 statute miles, on a good day), they could also detect direction.

Acoustic mirrors had a limited effectiveness, and the increasing speed of aircraft in the 1930s meant that they would already be too close to deal with by the time they had been detected. The development of radar put an end to further experimentation with the technique. Nevertheless, there were long-lasting benefits. The acoustic mirror programme, led by Dr William Sansome Tucker, had given Britain the methodology to use interconnected stations to pin point the position of an enemy in the sky. The system they developed for linking the ranging stations and plotting aircraft movements was given to the early radar team and contributed to their success in WW2; although the British radar was less sophisticated than the German system, the British system was used more successfully.

WWI & WII Devices Were Definitely Interesting

WWII Acoustic Location Devices
The 1920's Czech's had an interesting approach

WWII Acoustic Location Devices
Set up to determine altitude of the incoming noise

WWII Acoustic Location Devices
Circa 1921

WWII Acoustic Location Devices
At the center of things

WWII Acoustic Location Devices
German designs were quite advanced

WWII Acoustic Location Devices

WWII Acoustic Location Devices

WWII Acoustic Location Devices

WWII Acoustic Location Devices

WWII Acoustic Location Devices
1943 US Army sound locator

WWII Acoustic Location Devices

WWII Acoustic Location Devices

WWII Acoustic Location Devices
WWI devices

WWII Acoustic Location Devices
The French collected sound from almost 100 collectors

WWII Acoustic Location Devices

WWII Acoustic Location Devices

WWII Acoustic Location Devices

WWII Acoustic Location Devices

Japanese Devices

Japanese WWII Acoustic Listening Devices
With the Emperor

Did you know? - The Japanese war tuba is a colloquial name sometimes applied to Imperial Japanese Army acoustic locators due to the visual resemblance to the musical tuba. The name derived from a misidentification, possibly in jest, of a historical photo from the 1930s featuring the Japanese emperor Shôwa inspecting the acoustic locators with anti-aircraft guns in the background. Acoustic location was used from mid-World War I to the early years of World War II for the passive detection of aircraft by picking up the noise of the engines. It was rendered obsolete before and during World War II by the introduction of radar, which was far more effective