So I know that altitude affects the speed of sound because of temperature differentials in the atmosphere, but I am curious what else affects how we hear planes overhead?

When a plane flies overhead, you dont hear a very constant filter at all frequency bands. It seems that lower frequencies are more consistent, where high frequencies seems to fade in and out, sounding much like a low pass filter.

Is this the product of the temperature differentials between you and the plane changing as the plane moves, or are there other factors? Does moving air affect the sound in any way?

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    $\begingroup$ I'm voting to close this question as off-topic because it's not about aviation, but about physics. $\endgroup$ – Federico May 4 '15 at 18:34
  • $\begingroup$ @Federico Hmm... the "or are there other factors" may involve aviation, but specifically how altitude affects sound is more of a pure physics question. I'm not completely certain this is off-topic, but it does seem likely that it could get a better answer at Physics. $\endgroup$ – reirab May 4 '15 at 19:00
  • $\begingroup$ I'm not sure if this is so off-topic for aviation, Sound and its effects are very important for aviation. For example, I studied Aerospace Engineering, and I had several classes on sound generation, sound propagation, and noise mitigation. $\endgroup$ – ROIMaison May 5 '15 at 9:05

The answer to your question has a lot to do with how waves generated by a moving object propagate. You can see a full explanation here but the short answer is the Doppler Effect which causes pitch to change as the object moves buy you.

Here is a nice explanation


My knowledge is a bit rusty but basically you are talking about a mechanical wave propagating through a fluid (the atmosphere) which will absorb some of the energy (eventually all of it). I would also thing that as the speed of sound changes the frequency of the wave would change much like the changes light has when it crosses different mediums.

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  • $\begingroup$ hahah, that is an excellent clip :D I should have specified a bit more. I am also aware of the doppler effect. I am more curious about the filters and sound reflection within the atmosphere that produce the sense of distance for planes. I believe it is a combination of things, but I am not certain. I am attempting to build a DSP simulation of an airplane different altitudes $\endgroup$ – cosmikwolf May 4 '15 at 19:01

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