Boeing’s engine chevrons have long become one of the easiest visual clues separating aircraft like the Boeing 787, 747-8, and 737 MAX from many rivals. Those serrated nacelle edges look dramatic, but they were never added for just style alone. They were introduced to solve a very specific problem. Modern high-bypass turbofans may be far quieter than older jets, yet the violent mixing of hot core flow, cooler bypass air, and the surrounding atmosphere still creates a major share of engine noise.