Wind blowing across suspended power lines may cause the power lines to vibrate at their natural frequency. This often produces audible sound waves. This phenomenon, often called an Aeolian harp, is an example of (1) diffraction (3) refraction (2) the Doppler effect (4) resonance
(4) resonance. Resonance is a phenomenon that occurs when a vibrating system or force (the force from the wind particles in this case) drives another system to oscillate with greater amplitude at its resonant frequency.