The Trade-Off Between Efficiency and Noisiness in Blade Design for Prop Props

There's traditionally a trade-off between noisiness and efficiency when it comes to propeller design. More blades, because just the flow of the air to air around reduces the blade tip vortices. And so more blades are there, that's why they're less noisy, but they're also less efficient. A recent study was able to create a blade that has a significant like multi decibel reduction in noisiness with only a small hit and efficiency.