When you blow your horn while driving toward a stationary listener, an increase in frequency of the horn is he

Question

When you blow your horn while driving toward a stationary listener, an increase in frequency of the horn is heard by the listener. Would the listener hear an increase in the frequency of the horn if he were also in a car traveling at the same speed in the same direction as you are? Explain.

Answer 1

Doppler effect

No

The formula goes something like this

Fo= intial frequency
F=Heard frequency
V=speed of sound
Vs=speed of source
Vo=speed of observer

F=Fo*(V-Vs)/(V-Vo)

so lets plug in some make believe numbers.

Fo=10...... V=100.......Vs=30...... Vo=30

F=10*(100-30)/(100-30)=10

So you see the observed frequency doesn't change

Answer 2

No.

If you're driving that same car and throw a tennis ball at someone, they will feel the force of the throw AND the force from the car's momentum. If you throw the ball to another car moving in the same speed and direction, only the force of the throw is felt.

The sound is a series of pressure waves; a moving sound emitter compresses these waves, adding energy and increasing the frequency. If the listener is also moving away, the compression is cancelled out.

Increasing the frequency by other means, however, will not make the car go faster. I just thought I should point that out.

Answer 3

The Doppler Effect

Yes, the determination of the Resultant frequency is the relative velocity.... so 50m/s - 50m/s = 0 and the listener in the second car would hear the Resultant frequency the same as a listener in the first car.

RF= F x (v-vsource)/(v-vobserver)

As the listener travels away from the source, the resultant (or heard) frequency is lessened, and when travelling towards the source, the RF is increased.

Answer 4

No. The increase in frequency is due to the car traveling toward the listener. If the listener is traveling at the same rate and the same direction of the horn, there would be no increase in frequency.

Answer 5

If the listener were travelling the same speed as the source of the sound, he would still notice the shift in frequency, due to the doppler effect. When talking about sound, and other waves that are transmitted by a medium (in this case the air), the doppler effect has to do with the relative speed between the source of the sound and the medium through which it is transmitted (air).

On the other hand, if we were talking about light, or other waveforms independent of a transmission medium, the doppler effect has to do with relative speeds between the source and the observer.

Answer 6

Sound propagates at a speed of about 1,100 feet per second in air at sea level and the sound is in the form of sinusoidal waves at a frequency depending upon the source (horn). In a way, sound spreads like the ripples on a still mill pond when you throw in a stone. If a swimmer swims toward the stone, he/she will encounter more ripples per second than if standing still and less ripples per second if swimming away from the stone. The pitch of the "sound" depends on the ripples per second encountered.

In your example, the driver is moving much slower than the sound waves (which are traveling at Mach one, like a jet plane!). If the car was still the pitch of the horn would be F1 (frequency 1). If the car approaches the listner the pitch increases to F2 because each new wave originates closer and closer to the listener and has less far to travel. If the driver and listener are traveling in the same direction at the same speed, the drivers pitch increases from F1 to F2 but the listener's motion shifts the pitch back from F2 to F1 because the time it takes each wave to travel to the listener is the same as if both were at rest. The distance between them is constant if they are at rest or traveling at the same speed in the same direction. Of course if both the driver and the listener are traveling at the speed of sound in the same direction, the sound would never reach the listener.

Answer 7

This is the Doppler Effect. If someone were driving at the same speed and same direction as you, they would hear the same horn you would hear (ignoring insignificant variables). Think about it this way. Sound waves are similar to ocean waves. Say you're driving in a boat AGAINST the waves (meaning they're coming at you). You're going to hit the waves with a higher frequency. If you're driving WITH the waves, you will hit them at a lower frequency. This is how the doppler effect works in terms of sound.

However, if you're both going in the same speed in the same direction, nobody's working with or against the waves, so it will be heard as normal. It's like if oyu're driving in a car and the one next to you is goingthe same speed, it looks like it's stopped, when actually it's going as fast as you. The sound will sound the same becuase both you and the sound are traveling at teh same speed in the same direction.

Hope that helped. Any confusion? Email me.

Answer 8

http://encyclopedia.thefreedictionary.com/Doppler+effect
http://encyclopedia.thefreedictionary.com/Frequency+(sound)

As you're approaching an object it will sound sped up. As you reach it and match its speed it will sound normal. As you move away from it, it will slow down.

Consider its frequency relative to the observer. Let's say the wave was a physical thing. Someone made a wave out of steel, and you could sit and look at it, or walk away from it, or walk toward it, parallel to it.

As you walk toward the center of it, it seems to keep getting larger, and the faster you move by it the faster the crests and valleys move by. This is shifting its frequency, making appear to move faster and faster and getting bigger and bigger, the closer you get. As you approach the middleand slow down, you see the wave as "normal" as you approach its speed. As you start walkign away, it seems to start getting smaller and smaller or weaker and weaker... This is where it seems to slow down its oscillation.

Maybe not the best analogy... Basically the faster you go the more peaks and valleys you see, increasing its frequency. The slower you go, the fewer peaks and valleys you see, thus the slower the frequence of change. If you were to "catch up to it" you'd see/hear it going at whatever its normal speed was...

Answer 9

Not unless that's the law in your state. Your horn is to be used as an emergency warning device only.

Answer 10

I agree with Bren except for a little correction.

You & the SOUND are not travelling in the same direction at the same speed (as mentioned), its you & SOURCE of sound that is travelling at the same speed. Speed of sound is way too fast & only supersonic vehicles can make you travel at that speed.