The effect of the sound getting quicker and louder as the source approaches you is known as the Doppler effect. It is not caused because the beat is changing or the volume getting louder. The frequency of the waves reaching you get higher as the source approaches, it is equal at the instant it is right next to you, and lower after it passes.

The Doppler effect happens because sound moves in waves, called sound waves. Sound moves through the air in sound waves. Let's say you are visiting the …

Doppler effect. Radiation emitted from a source and received by an observer that are in relative motion to each other appears to be of a lower or higher frequency than if there were no relative motion between source and observer. If the relative motion between source and receiver causes motion toward each other, the frequency is shifted upward (sometimes called blue shifted).

The Doppler effect is evidence that the universe is expanding. Edwin Hubble used the Doppler effect to prove that the universe is expanding. Hubble noticed that the light from distant galaxies was shifted toward lower frequencies to the red end of the spectrum. When stars or galaxies are moving away from us, we see their colour as red-shifted.

The Doppler effect, named after Christian Andreas Doppler, is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. For waves, such as sound waves, that propagate in a wave medium, the velocity of the observer and the source are reckoned relative to the medium in which the waves are transmitted.

The Doppler effect is also called the Doppler shift. It is the change in frequency of a wave corresponding to an observer who is moving relative to the wave source. This effect was named after the Austrian physicist Christian Doppler, who described the Doppler principle in 1842. A common example of the Doppler effect in sound is the altering of pitch heard when a bus …