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Buy AumSum Merchandise: Why Are Helicopters So Loud? The primary reason is blade-vortex interaction. Let me explain. When the main rotor of a helicopter starts rotating, the blades start spinning. Due to this spinning, air pressure above the blades starts dropping while air pressure below the blades starts increasing. As a result, there exists a huge air pressure difference. Now, air from high pressure area starts moving to low pressure area. This produces a lift which causes the helicopter to rise. But, it also leads to the creation of various airflows. One of them is a vortex. This vortex is generated by the tip of a rotor blade. When this vortex hits the next advancing blade, the blade vibrates. This is called blade-vortex interaction. The vibrations of the blade generate a loud sound. Hence, helicopters are so Noisy. References:
