Timber blades are generally quieter than metal blades because they have a better cross-sectional profile to generate non-turbulent airflow. Metal blades with a sharp leading edge create more turbulence resulting in a whirr reminiscent of a helicopter. Plastic blades (all-weather polymer) are typically the best option as they are generally quieter than metal blades, however can be moulded into more aerodynamic shapes and therefore often provide better airflow than timber blades.