A closer look
Automobile horns manufactured in the United States and Europe are overwhelmingly tuned to the key of F, specifically F or F-sharp, because traffic psychologists discovered that this pitch pierces through the ambient low-frequency rumble of road noise most effectively. In the early days of motoring, horns were manually squeezed bulbs that produced polite, varied toots, but modern traffic congestion demanded a standardized acoustic assault that would trigger an immediate, adrenaline-fueled startle response in nearby humans. Car manufacturers literally employ sound engineers to craft the exact decibel and pitch required to induce maximum auditory panic. It is a brilliant piece of psychoacoustic engineering that we mostly just use to aggressively express our profound irritation at the driver who takes too long to react to a green light
