Suppose there is a man standing on a platform and a man inside a train. They started talking with each other. We know speed of sound-340m/s, so when the train starts moving will the speed of reception of the dialogues also change? (like 340m/s + Speed of train).

So will be able to hear faster if someone is moving towards you and speaking??


closed as off-topic by elemtilas, Elmy, Separatrix, StephenG, Renan Sep 17 '18 at 14:44

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about worldbuilding, within the scope defined in the help center." – elemtilas, Elmy, Separatrix, StephenG, Renan
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 2
    $\begingroup$ Hi RajEev! Welcome to Worldbuilding SE! This is a Q&A forum about making fictional worlds and settings for stories. Please take a look at the tour and help center to get an idea of what kinds of questions are allowed and not allowed in this forum. Your question is basically a physics question and might best be explored in the Physics SE. I don't see any worldbuilding context that would make this question viable here. $\endgroup$ – elemtilas Sep 17 '18 at 14:09
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    $\begingroup$ Consider: If it did, then what would be the effect on a pilot of a supersonic jet speaking into their microphone (which is located in front of their mouth)? Now, what does the answer to that tell us? $\endgroup$ – a CVn Sep 17 '18 at 14:16
  • $\begingroup$ I don't see any worldbuilding context that would make this question viable here either, but for answers, see en.wikipedia.org/wiki/Doppler_effect $\endgroup$ – GretchenV Sep 17 '18 at 14:19
  • $\begingroup$ Compare a train travelling at 50 mph to the speed of sound 767 mph. Technically, the answer to your question is "yes." However, it's also irrelevant. A train would need to be travelling many times faster than the fastest train today to make a difference - assuming the volume of speech was enough to be heard over the required distance. That amplitude is your real problem. The average shout can only be heard clearly, what, a couple of hundred feet away? At the speeds we're talking the train would have passed long before you got your shout out. $\endgroup$ – JBH Sep 17 '18 at 14:22

So I'm not sure if I am fully answering your question because of the way it is being asked. If someone is moving towards another individual, of course there will be less time between when the sender speaks and the receiver receives. So yes, I guess you will hear the message faster if you are approaching each other than if you were both stationary. But this is only due to the fact that the other person is now closer.

But maybe what you really mean to ask is what would the differences in sound be. The Doppler Effect will come in to play, and if the relative speed is fast enough, you will hear a difference in pitch of the other person speaking. This is a purposeful design in things like sirens because as the ambulance is approaching you, the whine gets higher, which attracts your attention more. Frequencies and modulations are picked to make this effect even more noticeable to the human ear.


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