Via badscience.net, the Japanese War Tuba Hack! (Or maybe we’ll call it “improve sound localisation by increasing interaural distance” or something).
Similarly the way your visual system calculates depth from the different images that your two eyes get, you use the difference in when sounds arrive at your ears to calculate their location. Bigger distance between the ears means bigger differences in arrival times, means more sensitivity in detecting sound location. How do you increase the distance between the ears? Ear horns! Don’t they look great?