How does Doppler Effect change the sound made by moving vehicles?

Question

Physics Scavenger Hunt

Answer 1

If an object is moving toward you, the frequency of the soundwaves is higher, therefore a higher pitch sound is produced. If it is moving away from you, the frequency is lower, thus a lower pitch sound. Think of a train rolling toward you blowing its horn, the pitch of the horn changes noticably just as it passes you.

Answer 2

The siren on a passing emergency vehicle will start out higher than its stationary pitch, slide down as it passes, and continue lower than its stationary pitch as it recedes from the observer. Astronomer John Dobson explained the effect thus:

"The reason the siren slides is because it doesn't hit you."

In other words, if the siren approached the observer directly, the pitch would remain constant (as vs, r is only the radial component) until the vehicle hit him, and then immediately jump to a new lower pitch. The difference between the higher pitch and rest pitch would be the same as the lower pitch and rest pitch. Because the vehicle passes by the observer, the radial velocity does not remain constant, but instead varies as a function of the angle between his line of sight and the siren's velocity:

v_{s, r}=v_s\cdot \cos{\theta}

where vs is the velocity of the object (source of waves) with respect to the medium, and θ is the angle between the object's forward velocity and the line of sight from the object to the observer.

Answer 3

As the object making the sound gets closer, the sound waves get compressed between him and you.This makes the sound more high pitched. As it moves away, the sound waves have more space to travel to him and you, making the sound lower.

Answer 4

The the two prepare with the comparable theory of waves and relative positions. because of the fact the article comes closer, the waves seem to be shorter because of the fact they are passing you swifter. while it gets farther, the waves look longer because of the fact they take longer to pass you. you could think of it like the wave has the extra desirable velocity of the article while it passes you.

Answer 5

The frequeny increases if the source and observer get closer, and decreases if they move apart.