I could be wrong here, but I think quieter propellers may be more energy efficient. Since noise is just energy, it's wasted on noise rather than propulsion. C

I could be wrong here, but I think quieter propellers may be more energy efficient. Since noise is just energy, it's wasted on noise rather than propulsion. Case in point: Formula 1 engines this year are turbo, and are much quieter. Many fans complain because they are too quiet! But they are more efficient.