The pinna’s convoluted shape exists to encode sound direction via reflections

Evidence

The shape of our pinna is simply ridiculous—unless it has a purpose. The pinna takes its curious shape in order to help us localize sound (figure 21.2). High frequencies, above 2000 or 3000 Hz, can reflect—perhaps multiple times—off the structures of the pinna in a way that differs according to the azimuth, the angle of approach above the horizon. When these reflected waves make it into the ear canal, they carry information about their original direction, in the form of repetition peaks and valleys. — Eric J. Heller, Why You Hear What You Hear- An…, 1930

Categorization

• DEFINE: Clarifies that ‘azimuth’ here refers to angle of approach above the horizon, and introduces how pinna shape functions as a direction-encoding structure.