The whine of a motorclye's engine is changed when it passes by a stationary person compared to someone who is moving in the opposite direction. The same thing happens when someone is closer or farther away from the motorcycle The shift in the engines pitch is higher the closer you are and lower the farther you are. This effect is known as the Doppler effect.
The Doppler shift is caused by how close or how far away you are to a stationary object. A car that is speeding by two pedestrians on opposite sides will have the same wave lengths. Meanwhile a car going the same speed would have different sized wavelengths depending on how close one pedestrian is from the other. The Doppler shift is a sensory illusion.
Created with images by skeeze - "military jet flight flying" • Advait Berde - "untitled image" • paulbr75 - "car engine engine motor" • skeeze - "sound barrier broken navy jet"