This happen because of what is called Doppler effect and it occur you who is the receiver of the sound waves is in motion and the source of the wave is stagnant.
Sound waves is a form of transverse waves in which there is vibrations and compression of particles traveling through a medium thereby transferring energy from one medium to another.
Therefore, This happen because of what is called Doppler effect and it occur you who is the receiver of the sound waves is in motion and the source of the wave is stagnant.
Learn more about sound waves below.
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