Your ears are usually at different heights and have slightly different shapes to help you find where sounds come from.

Most people think their ears are perfectly level, but they are often offset by a few millimeters. This asymmetry is a key part of how humans locate sound in a 3D space. When a sound occurs, it hits one ear slightly before the other and at a different volume. These are called interaural time and level differences.The brain can detect time differences as small as 10 microseconds. It also looks at how sound waves bounce off the folds of your outer ear, which is called the pinna. These folds filter the sound frequencies based on the direction they come from. This helps the brain decide if a sound is high up or low on the ground.In 1907, physicist Lord Rayleigh explained these concepts in his Duplex Theory. Without two ears at slightly different positions, humans would struggle with the cone of confusion. This is a problem where a person cannot tell if a sound is directly in front of them or directly behind them.The auditory cortex in the brain processes these signals instantly to create a map of your surroundings. Humans are so good at this that they can detect a change in sound position of only 1 to 2 degrees. This ability was important for early humans to hear predators moving in the wild. Your brain also accounts for how your head and shoulders block or reflect sound waves.