Basically, they are “ear binoculars”.
Japanese War Tubas, only a few decades ago, were the very pinnacle of modern technology, and your best bet for locating an enemy in the distance, or in the dark (that?s Hirohito on the right). … We can locate objects with our ears, using the difference in volume between our left and right ear, but more important is the time delay between the sound hitting one ear and then hitting the other. This is possible because sound travels so incredibly slowly, only 330 metres (or 1000 feet) per second. Thinking out loud, that means sound travels one foot in one millisecond, so if your ears are about six inches apart, the sound coming from your right will hit your right ear about half a millisecond before it hits your left ear. A millisecond is quite a long time: in a piece of music, for example, you can spot notes that are only a few milliseconds out as being in the wrong place.