**Appendix B**

Noise measurement of wind turbines. The noise generated by wind turbines is itself a kind of sound, so it has all the characteristics of a sound. The vibration of an object causes a sound. Energy is then transmitted through a given elastic medium in the form of sound waves. Therefore, all the factors that cause the vibration of a rotating machine body or cause the pressure field of a transmission medium to change are all mechanical equipment noise sources. When a wind generator is in regular operation, the blades generate periodic noise due to the pulsating force of the outlet's uneven flow. On the other hand, due to the uneven distribution of the pressure on the blades themselves, the surrounding gas and components' disturbance during rotation also constitutes rotational noise. The turbulent pressure distribution on the blades causes turbulence noise due to the turbulent flow, airflow, and vortex shedding generated when the gas flows through the blade. The low-frequency sound is generated by the wind turbine results from this. Large-scale wind turbines have a small number of diaphragms. Under regular operation, there are not many turns, so low-frequency sounds occur. If one measures the fundamental frequency *f* (Hz) of the noise of the wind turbine, then the following relationship exists between the speed of the wind fan *R* (rpm) and the wind turbine blade *Z* (pieces): *f* = *RZ* <sup>60</sup> (Hz).
