If you are standing at a street corner, can anyone explain the reason that the sound of a car coming toward you sounds different than after it passes you? The same is true for police sirens and motorcycles etc., but why is this?
2007-09-19 13:43:27 · 4 answers · asked by Boomer 5 in Science & Mathematics ➔ Physics
Sound waves travel in the form of compressions and rarefactions of the air particles. The wavelength is the total distance occuppied by one compression and one rarefaction, just like the crest and trough. The sound produced by any moving object will have a change in wavelength. From an approaching source the wavelength will be shorter than the actual wave produced. Hence the soundis heard more shrilling. Similarly, the sound produced by a receding source will be of longer wavelength and the hearer will have an apparent rough sound experience, This effect is called DOPPLER EFFECT. THe same experience will be there in a railway platform for an observer, -high frequency sound from an approaching train and a low frequency sound from a receding train.
2007-09-19 16:08:45 · answer #1 · answered by Joymash 6 · 0⤊ 0⤋
Consider the sound to be made of a series of pulses that whack your eardrum. If the sound source is standing still, they hit your ear at a particular rate, resulting in the tone you hear.
Now, if the source is moving towards you, pulse 2 happens when the source is closer than when pulse 1 happened. So the two pulses will hit your ear with less time in between, because the second one has a shorter travel time.
if the source is moving away from you, pulse 2 will have to travel farther than pulse 1, and there will be more time between pulses.
What we hear as pitch is a measure of how far apart the pulses are. Closer together is higher pitched, farther apart is lower pitched. And that is the previously-mentioned Doppler effect (after a guy named Doppler, not because it involves doubling in German).
2007-09-19 20:56:12 · answer #2 · answered by Dvandom 6 · 1⤊ 0⤋
it is because as the sound source is far away from you the in one second you hear a less number of sound waves,i.e.,the frequency of the sound heard is less due to which the pitch is also LOW while when the source of sound is nearer the frequency is increased and thus the pitch is higher thus we hear a shriller sound.The wavelength in both cases is the same and the frequency only changes
2007-09-19 22:14:38 · answer #3 · answered by mihir 2 · 1⤊ 0⤋
It is due to Doppler Effect.the apparent frequency of a source of sound increases when source approaches the observer and vice versa.
2007-09-19 20:51:37 · answer #4 · answered by Anonymous · 1⤊ 0⤋