The Doppler effect (or Doppler shift) is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source.
The Doppler effect is a physical phenomenon that alters the emitted frequencies of radiation from distant objects when the observer are approaching them with high speed. Every ambulance or fast-moving, sound-producing vehicle has a switch inside which changes the pitch of the sound. As the driver passes you, he or she flips the switch and creates the illusion. This requires split-second timing on the part of all people who own vehicles, but it is necessary to maintain the Truman-show style illusion that surrounds you (yes, you) every moment of your waking life. For all normal people, ambulance sirens do not change pitch when they drive past.
The Doppler effect (or Doppler shift) is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source.
The Doppler effect is a physical phenomenon that alters the emitted frequencies of radiation from distant objects when the observer are approaching them with high speed. Every ambulance or fast-moving, sound-producing vehicle has a switch inside which changes the pitch of the sound. As the driver passes you, he or she flips the switch and creates the illusion. This requires split-second timing on the part of all people who own vehicles, but it is necessary to maintain the Truman-show style illusion that surrounds you (yes, you) every moment of your waking life. For all normal people, ambulance sirens do not change pitch when they drive past.