An engineeer in a moving train blows the train horn. The train is moving away from a person standing on the?

Question

ground. Compared to the frequency of the sound that the engineer hears, the person standing on the ground hears.

A. the same wavelength

B. More variation in tone

C. Greater amplitude

D. Lower frequency

Please, help me and tell me WHY?

Thank you

Answer 1

Have you every listened to something like siren, or even a load car radio from the guy stopped next to you.  As they move away from you, what happens?  Normally not "A". the sound does not stay the same.  Also not "C", it does not get louder as the sound moves away.  It also would not vary in tone as it moved away (B).  What it should do is get lower - which is answer D.  The lower tones with the longest wavelength will be the last to fade out.  

So the answer is D.

Answer 2

D.

because as the train moves away, it stretches the sound waves, putting more distance between the waves...

Answer 3

B.  Motion affects the soundwaves(like a flag in the breeze)

Usually the pitch seems to drop.

Answer 4

The eingineer didnt hear as much as the guy standing on the ground because he has listened to so many train horns for so long that he has lost half his hearing due to noisy work environments that the railroads could have mitigated 50 years ago and didnt have enough compassion for their employees.

Wait, what was the question, i got sidetracked again.

Answer 5

Skidderback is correct that it's D, and it's the DOPPLER effect, but the explaination is off a bit...

The horn is actually blowing at several different frequencies, BUT for the sake of arguement, we'll SAY it's blowing at ONE frequency 500Hz:

The engineer will ALWAYS hear the 500Hz tone (Vo)... if you're AHEAD of the train you'll hear a tone about 510Hz and BEHIND the train you'll hear a tone of about 490Hz.

THIS occurs because as the train travels AHEAD, the sound waves are compressed slightly and those behind the train hear sound waves that are slightly LONGER (therefore lower)

I know because I taught doppler regarding Anti-Submarine Warfare in the Navy for years

Answer 6

D.

But, in this case, the "D" should stand for "Doppler Effect" since the sound source is moving.  A bit complicated, so lets just say, low frequency sound waves are longer and travel further, as well as having a tendency to pass around obstacles.  Higher frequencies do not negotiate obstacles well and tend more to "reflect" off of surfaces, with a portion of the energy absorbed by that object (refraction) and dissipating the difference of that absorbed energy as heat.

If you've ever been to a concert or somewhere where a band is playing and you leave early or head to the restroom or something, the last notes you hear when walking away are the low frequency notes.

The human ear has the ability to detect sound between 20Hz (Hertz, or cycles per second) and 20kHz (20,000 cycles per second).  Anything below 150Hz is considered low frequency.  It is also non-directional, which is a plus when running a sound system, since the subs do not have to be a part of the stereo field, allowing for easier and more economical mono operation and reproduction of the low frequency sound waves from drums and bass instruments.

Also in play is the "Inverse Square Law."  Simply put, the dB levels (dB = Decibel, in this case a measurement of sound pressure) drop off exponentially as the distance from the source increases.

Although, Rango's description below is equally as plausible...

A very good question.