If sound is a longitudinal wave, why can we hear it if our ears aren't aligned with the propagation...












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If a sound wave travels to the right, then the air molecules inside only vibrate left and right, because sound is a longitudinal wave. This is only a one-dimensional motion. If our ears are oriented perpendicular to this oscillation, e.g. if they are pointing straight up, how can we hear it?










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  • 2




    $begingroup$
    it is not that simple . see hyperphysics.phy-astr.gsu.edu/hbase/Sound/sprop.html and links
    $endgroup$
    – anna v
    2 days ago






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    $begingroup$
    This website has some nice animations to show the three dimensional nature of longitudinal sound waves.
    $endgroup$
    – Farcher
    yesterday






  • 2




    $begingroup$
    Here's another pretty good explanation with animations, courtesy of the University of Southampton.
    $endgroup$
    – Ilmari Karonen
    yesterday






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    $begingroup$
    Almost everybody commenting or answering has completely misinterpreted the question. There is no need to rehash the entirety of an introductory course of waves, in 10 little bits and pieces, when the actual question is much more specific.
    $endgroup$
    – knzhou
    19 hours ago






  • 1




    $begingroup$
    @IlmariKaronen OP replied in several comments below, annoyed that answerers had misinterpreted his question. I just tried to condense them in a more digestable form.
    $endgroup$
    – knzhou
    11 hours ago
















13












$begingroup$


If a sound wave travels to the right, then the air molecules inside only vibrate left and right, because sound is a longitudinal wave. This is only a one-dimensional motion. If our ears are oriented perpendicular to this oscillation, e.g. if they are pointing straight up, how can we hear it?










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New contributor




Sarvesh Thiruppathi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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  • 2




    $begingroup$
    it is not that simple . see hyperphysics.phy-astr.gsu.edu/hbase/Sound/sprop.html and links
    $endgroup$
    – anna v
    2 days ago






  • 2




    $begingroup$
    This website has some nice animations to show the three dimensional nature of longitudinal sound waves.
    $endgroup$
    – Farcher
    yesterday






  • 2




    $begingroup$
    Here's another pretty good explanation with animations, courtesy of the University of Southampton.
    $endgroup$
    – Ilmari Karonen
    yesterday






  • 2




    $begingroup$
    Almost everybody commenting or answering has completely misinterpreted the question. There is no need to rehash the entirety of an introductory course of waves, in 10 little bits and pieces, when the actual question is much more specific.
    $endgroup$
    – knzhou
    19 hours ago






  • 1




    $begingroup$
    @IlmariKaronen OP replied in several comments below, annoyed that answerers had misinterpreted his question. I just tried to condense them in a more digestable form.
    $endgroup$
    – knzhou
    11 hours ago














13












13








13


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$begingroup$


If a sound wave travels to the right, then the air molecules inside only vibrate left and right, because sound is a longitudinal wave. This is only a one-dimensional motion. If our ears are oriented perpendicular to this oscillation, e.g. if they are pointing straight up, how can we hear it?










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New contributor




Sarvesh Thiruppathi is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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$endgroup$




If a sound wave travels to the right, then the air molecules inside only vibrate left and right, because sound is a longitudinal wave. This is only a one-dimensional motion. If our ears are oriented perpendicular to this oscillation, e.g. if they are pointing straight up, how can we hear it?







waves acoustics






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edited 19 hours ago









knzhou

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asked 2 days ago









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  • 2




    $begingroup$
    it is not that simple . see hyperphysics.phy-astr.gsu.edu/hbase/Sound/sprop.html and links
    $endgroup$
    – anna v
    2 days ago






  • 2




    $begingroup$
    This website has some nice animations to show the three dimensional nature of longitudinal sound waves.
    $endgroup$
    – Farcher
    yesterday






  • 2




    $begingroup$
    Here's another pretty good explanation with animations, courtesy of the University of Southampton.
    $endgroup$
    – Ilmari Karonen
    yesterday






  • 2




    $begingroup$
    Almost everybody commenting or answering has completely misinterpreted the question. There is no need to rehash the entirety of an introductory course of waves, in 10 little bits and pieces, when the actual question is much more specific.
    $endgroup$
    – knzhou
    19 hours ago






  • 1




    $begingroup$
    @IlmariKaronen OP replied in several comments below, annoyed that answerers had misinterpreted his question. I just tried to condense them in a more digestable form.
    $endgroup$
    – knzhou
    11 hours ago














  • 2




    $begingroup$
    it is not that simple . see hyperphysics.phy-astr.gsu.edu/hbase/Sound/sprop.html and links
    $endgroup$
    – anna v
    2 days ago






  • 2




    $begingroup$
    This website has some nice animations to show the three dimensional nature of longitudinal sound waves.
    $endgroup$
    – Farcher
    yesterday






  • 2




    $begingroup$
    Here's another pretty good explanation with animations, courtesy of the University of Southampton.
    $endgroup$
    – Ilmari Karonen
    yesterday






  • 2




    $begingroup$
    Almost everybody commenting or answering has completely misinterpreted the question. There is no need to rehash the entirety of an introductory course of waves, in 10 little bits and pieces, when the actual question is much more specific.
    $endgroup$
    – knzhou
    19 hours ago






  • 1




    $begingroup$
    @IlmariKaronen OP replied in several comments below, annoyed that answerers had misinterpreted his question. I just tried to condense them in a more digestable form.
    $endgroup$
    – knzhou
    11 hours ago








2




2




$begingroup$
it is not that simple . see hyperphysics.phy-astr.gsu.edu/hbase/Sound/sprop.html and links
$endgroup$
– anna v
2 days ago




$begingroup$
it is not that simple . see hyperphysics.phy-astr.gsu.edu/hbase/Sound/sprop.html and links
$endgroup$
– anna v
2 days ago




2




2




$begingroup$
This website has some nice animations to show the three dimensional nature of longitudinal sound waves.
$endgroup$
– Farcher
yesterday




$begingroup$
This website has some nice animations to show the three dimensional nature of longitudinal sound waves.
$endgroup$
– Farcher
yesterday




2




2




$begingroup$
Here's another pretty good explanation with animations, courtesy of the University of Southampton.
$endgroup$
– Ilmari Karonen
yesterday




$begingroup$
Here's another pretty good explanation with animations, courtesy of the University of Southampton.
$endgroup$
– Ilmari Karonen
yesterday




2




2




$begingroup$
Almost everybody commenting or answering has completely misinterpreted the question. There is no need to rehash the entirety of an introductory course of waves, in 10 little bits and pieces, when the actual question is much more specific.
$endgroup$
– knzhou
19 hours ago




$begingroup$
Almost everybody commenting or answering has completely misinterpreted the question. There is no need to rehash the entirety of an introductory course of waves, in 10 little bits and pieces, when the actual question is much more specific.
$endgroup$
– knzhou
19 hours ago




1




1




$begingroup$
@IlmariKaronen OP replied in several comments below, annoyed that answerers had misinterpreted his question. I just tried to condense them in a more digestable form.
$endgroup$
– knzhou
11 hours ago




$begingroup$
@IlmariKaronen OP replied in several comments below, annoyed that answerers had misinterpreted his question. I just tried to condense them in a more digestable form.
$endgroup$
– knzhou
11 hours ago










8 Answers
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vibration is only a one dimensional motion




This is not generally true. As a trivial example, one could the movements of water in a pond where a few small rocks have been tossed. The motion is definitely a wave behavior, and could even be called vibration, but it is most definitely not one dimensional.



Another potential example would be the vibrator on your phone, which vibrates in a circular manner.



But in the end, the key is that atoms in a sound wave don't vibrate "left and right." They are a longitudinal wave, in which particles move in the direction of the wave's motion and back.



So when something causes a sound, the waves propagate outward from the object creating the sound, as molecules of gas move away from the source and towards the source. This is typically a 3 dimensional pattern






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  • $begingroup$
    Hi, Thanks for the answer , it was really helpful. I still have doubt in the last paragraph of your answer. Can you explain it with more details. Also I never said that sound wave is a transverse wave , by left and right i meant to - and - fro.
    $endgroup$
    – Sarvesh Thiruppathi
    yesterday










  • $begingroup$
    Also , by 3 dimensional pattern , you mean a spherical kind of pattern , right ? But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre.
    $endgroup$
    – Sarvesh Thiruppathi
    yesterday






  • 1




    $begingroup$
    @SarveshThiruppathi In a sense, yes, as the particles move apart it creates a low pressure region, but this acts as the restoring force to bring them back together. These pressure variations are usually very small, though. For example, a typical conversation between 2 people generates pressure variations of about 2*10^-7 atmospheres.
    $endgroup$
    – Kyle
    yesterday










  • $begingroup$
    But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop
    $endgroup$
    – Sarvesh Thiruppathi
    yesterday






  • 2




    $begingroup$
    @SarveshThiruppathi If a sound wave is emitted for a long period of time, that means the source of the sound is vibrating for a long period of time. The wavelength would still be the same as if the same sound were emitted for a short period of time, so the vacuum you're imagining between waves wouldn't exist. What does make a difference is the volume (loudness) of the sound, which is why (roughly) there is a maximum possible volume which is reached when there is a vacuum between each wave.
    $endgroup$
    – dbmag9
    yesterday



















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Sound wave is not a transverse wave, as you thought. That means the vibration and the direction of propagation for sound wave are parallel. And the vibration is caused by difference in air pressure at different places. To the question "how I can listen to it" thats because the pressure difference propagates toward your ear and force your eardrum to vibrate.






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    Hi, I would like to point out two things from your answer. I never said a sound is a transverse wave. Also can you provide a explanation of how the sound wave propagated towards us.
    $endgroup$
    – Sarvesh Thiruppathi
    yesterday








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    Note, sound can be also a transverse wave, but only in solid materials (others don't have a shear stress). It has different properties than the longitudinal sound. This is how the internal properties of the Earth were discovered (liquid mantle, solid core). Also the electromagnetic and gravitational fields propagate as transverse waves.
    $endgroup$
    – peterh
    yesterday








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    "Sound wave is not a transverse wave, as you thought." This is nowhere in the OP's statement. As far as I'm concerned, this answer doesn't address the question at all.
    $endgroup$
    – knzhou
    19 hours ago










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    @knzhou I agree. -1. I'm not sure how this has gotten so many up votes
    $endgroup$
    – Aaron Stevens
    19 hours ago






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    @user10842694 I edited the question to make it a little clearer, but it was already clear in the first version that he wasn't asking "is sound a transverse wave". It blows my mind how half the answers here have answered that question instead.
    $endgroup$
    – knzhou
    19 hours ago



















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Sound travels outwards from a source in all directions. The waves that are set in motion are spherical.






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    Yes -- even though a 'speaker' may push air molecules in a certain direction, this just creates a volume of higher pressure air, which then expands in all directions.
    $endgroup$
    – amI
    yesterday



















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Re. from one of your comments: "But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre" and also this one: "But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop"



I think part of you confusion comes from this: Even with a longitudinal wave where the particle motion is parallel to the waves propagation direction, the particles do not travel with the wave. They only move back and forth along the direction of wave propagation. So the particles are not carried along with the wave. (It is obvious that this is true for a transverse wave.)



Referring to your original question, unless sound is focused into a beam it generally propagates equally in all directions. If it is focused into a beam and you were off to one side anything you hear would be due to sidelobes which are lower in amplitude than the main lobe and could be near zero.






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    The revised question, as I understand it, amounts to asking how it is possible for a sound wave propagating along (instead of towards) a wall with a small hole in it to generate any sound waves on the other side of the hole. I have drawn a diagram of what I believe happens in this case:



    Diagram of acoustic wave diffraction. A wall with a small hole in it divides the diagram horizontally in two halves.  In the top half of the diagram, a plane acoustic wave propagates horizontally past the hole.  In the bottom half, the hole acts as a point source for an expanding circular acoustic wave.



    The hole bleeds off some of the acoustic energy of the plane wave, and uses it to generate a circular wave on the other side of the wall, as if it were a point source. This is an example of diffraction. I know for certain that this is what happens when the plane wave propagates toward the hole, and I think in this simple case the angle between the plane wave and the wall would only affect the intensity of the circular wave, but I'm not sure of that and the Wikipedia page on diffraction doesn't say anything about the angle. Can anyone confirm?



    (N.B. A human's external ear has a much more complicated shape, which has evolved to efficiently gather sound waves passing the head in any direction and direct them into the ear canal, but the physical mechanism by which it does this is the same.)






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      You could use an explosion as a metaphor. The shockwaves "push" the air around in a spherical pattern, which then gets "sucked" back due to the low pressure left behind.



      In a sense, soundwaves are just very slow and small shockwaves.



      This video shows it really well.






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      • $begingroup$
        +1 - was going to post an answer explaining it via explosion. But... you might consider taking out "just very slow and small shockwaves" and replacing it with, "smaller, and usually either repeated or patterned shockwaves - a musical note is just small shockwaves in a specific timing pattern." or similar.
        $endgroup$
        – Kevin
        yesterday



















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      There is more than one way to describe the amplitude of a sound wave. You can describe it as a displacement, in which case it's a vector with units of meters. On the other hand, you can also describe it as a pressure, which is a scalar with SI units of pascals.



      It's possible to have a sound sensor whose response is proportional to the displacement, or one whose response is proportional to the pressure. The ear acts like the latter, because the eardrum is a membrane, and the membrane distorts in response to the pressure difference between the inner ear and the outside air. Therefore the ear is not sensitive to the direction in which the wave was propagating (although there are other cues that allow us to infer this for some frequencies, because we have binaural hearing).






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        While the mean air motion of the wave is in one direction (assuming a plane wave), the air molecules actually move in all directions. They are in local thermal equilibrium (due to frequent randomizing collisions), which is what gives meaning to pressure as the basis for modeling acoustics. This random molecular motion in all directions is at speeds of order the speed of sound, hundreds of meters per second.



        The mean motion (longitudinal) is an oscillating displacement of micrometers or less for typical sounds, at kilohertz frequencies, corresponding to a speed of millimeters per second at most. It can be much less for faint sounds. The ear is a remarkably sensitive detector!



        The ear canal is smaller than the wavelengths of audible sound. Thus, as sound passes by in any direction, the ear mainly responds to the pressure oscillations without regard to the direction of the wave. When a pressure peak surrounds the ear, air is (slightly) pumped into the ear, due to the random motions that equilibrate pressure. When a trough surrounds the ear, air is (slightly) sucked out of the ear. This happens at the frequency of the sound (say a thousand times per second), vibrating the eardrum.



        Zwol's answer correctly notes that this can be seen as an instance of diffraction. It is a limit in which the hole is so small that the pressure at any instant is nearly uniform over the hole, so diffraction through the hole is nearly independent of the incident angle.






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          8 Answers
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          8 Answers
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          active

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          15












          $begingroup$


          vibration is only a one dimensional motion




          This is not generally true. As a trivial example, one could the movements of water in a pond where a few small rocks have been tossed. The motion is definitely a wave behavior, and could even be called vibration, but it is most definitely not one dimensional.



          Another potential example would be the vibrator on your phone, which vibrates in a circular manner.



          But in the end, the key is that atoms in a sound wave don't vibrate "left and right." They are a longitudinal wave, in which particles move in the direction of the wave's motion and back.



          So when something causes a sound, the waves propagate outward from the object creating the sound, as molecules of gas move away from the source and towards the source. This is typically a 3 dimensional pattern






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Hi, Thanks for the answer , it was really helpful. I still have doubt in the last paragraph of your answer. Can you explain it with more details. Also I never said that sound wave is a transverse wave , by left and right i meant to - and - fro.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday










          • $begingroup$
            Also , by 3 dimensional pattern , you mean a spherical kind of pattern , right ? But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday






          • 1




            $begingroup$
            @SarveshThiruppathi In a sense, yes, as the particles move apart it creates a low pressure region, but this acts as the restoring force to bring them back together. These pressure variations are usually very small, though. For example, a typical conversation between 2 people generates pressure variations of about 2*10^-7 atmospheres.
            $endgroup$
            – Kyle
            yesterday










          • $begingroup$
            But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday






          • 2




            $begingroup$
            @SarveshThiruppathi If a sound wave is emitted for a long period of time, that means the source of the sound is vibrating for a long period of time. The wavelength would still be the same as if the same sound were emitted for a short period of time, so the vacuum you're imagining between waves wouldn't exist. What does make a difference is the volume (loudness) of the sound, which is why (roughly) there is a maximum possible volume which is reached when there is a vacuum between each wave.
            $endgroup$
            – dbmag9
            yesterday
















          15












          $begingroup$


          vibration is only a one dimensional motion




          This is not generally true. As a trivial example, one could the movements of water in a pond where a few small rocks have been tossed. The motion is definitely a wave behavior, and could even be called vibration, but it is most definitely not one dimensional.



          Another potential example would be the vibrator on your phone, which vibrates in a circular manner.



          But in the end, the key is that atoms in a sound wave don't vibrate "left and right." They are a longitudinal wave, in which particles move in the direction of the wave's motion and back.



          So when something causes a sound, the waves propagate outward from the object creating the sound, as molecules of gas move away from the source and towards the source. This is typically a 3 dimensional pattern






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Hi, Thanks for the answer , it was really helpful. I still have doubt in the last paragraph of your answer. Can you explain it with more details. Also I never said that sound wave is a transverse wave , by left and right i meant to - and - fro.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday










          • $begingroup$
            Also , by 3 dimensional pattern , you mean a spherical kind of pattern , right ? But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday






          • 1




            $begingroup$
            @SarveshThiruppathi In a sense, yes, as the particles move apart it creates a low pressure region, but this acts as the restoring force to bring them back together. These pressure variations are usually very small, though. For example, a typical conversation between 2 people generates pressure variations of about 2*10^-7 atmospheres.
            $endgroup$
            – Kyle
            yesterday










          • $begingroup$
            But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday






          • 2




            $begingroup$
            @SarveshThiruppathi If a sound wave is emitted for a long period of time, that means the source of the sound is vibrating for a long period of time. The wavelength would still be the same as if the same sound were emitted for a short period of time, so the vacuum you're imagining between waves wouldn't exist. What does make a difference is the volume (loudness) of the sound, which is why (roughly) there is a maximum possible volume which is reached when there is a vacuum between each wave.
            $endgroup$
            – dbmag9
            yesterday














          15












          15








          15





          $begingroup$


          vibration is only a one dimensional motion




          This is not generally true. As a trivial example, one could the movements of water in a pond where a few small rocks have been tossed. The motion is definitely a wave behavior, and could even be called vibration, but it is most definitely not one dimensional.



          Another potential example would be the vibrator on your phone, which vibrates in a circular manner.



          But in the end, the key is that atoms in a sound wave don't vibrate "left and right." They are a longitudinal wave, in which particles move in the direction of the wave's motion and back.



          So when something causes a sound, the waves propagate outward from the object creating the sound, as molecules of gas move away from the source and towards the source. This is typically a 3 dimensional pattern






          share|cite|improve this answer









          $endgroup$




          vibration is only a one dimensional motion




          This is not generally true. As a trivial example, one could the movements of water in a pond where a few small rocks have been tossed. The motion is definitely a wave behavior, and could even be called vibration, but it is most definitely not one dimensional.



          Another potential example would be the vibrator on your phone, which vibrates in a circular manner.



          But in the end, the key is that atoms in a sound wave don't vibrate "left and right." They are a longitudinal wave, in which particles move in the direction of the wave's motion and back.



          So when something causes a sound, the waves propagate outward from the object creating the sound, as molecules of gas move away from the source and towards the source. This is typically a 3 dimensional pattern







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered 2 days ago









          Cort AmmonCort Ammon

          23.6k34779




          23.6k34779












          • $begingroup$
            Hi, Thanks for the answer , it was really helpful. I still have doubt in the last paragraph of your answer. Can you explain it with more details. Also I never said that sound wave is a transverse wave , by left and right i meant to - and - fro.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday










          • $begingroup$
            Also , by 3 dimensional pattern , you mean a spherical kind of pattern , right ? But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday






          • 1




            $begingroup$
            @SarveshThiruppathi In a sense, yes, as the particles move apart it creates a low pressure region, but this acts as the restoring force to bring them back together. These pressure variations are usually very small, though. For example, a typical conversation between 2 people generates pressure variations of about 2*10^-7 atmospheres.
            $endgroup$
            – Kyle
            yesterday










          • $begingroup$
            But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday






          • 2




            $begingroup$
            @SarveshThiruppathi If a sound wave is emitted for a long period of time, that means the source of the sound is vibrating for a long period of time. The wavelength would still be the same as if the same sound were emitted for a short period of time, so the vacuum you're imagining between waves wouldn't exist. What does make a difference is the volume (loudness) of the sound, which is why (roughly) there is a maximum possible volume which is reached when there is a vacuum between each wave.
            $endgroup$
            – dbmag9
            yesterday


















          • $begingroup$
            Hi, Thanks for the answer , it was really helpful. I still have doubt in the last paragraph of your answer. Can you explain it with more details. Also I never said that sound wave is a transverse wave , by left and right i meant to - and - fro.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday










          • $begingroup$
            Also , by 3 dimensional pattern , you mean a spherical kind of pattern , right ? But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday






          • 1




            $begingroup$
            @SarveshThiruppathi In a sense, yes, as the particles move apart it creates a low pressure region, but this acts as the restoring force to bring them back together. These pressure variations are usually very small, though. For example, a typical conversation between 2 people generates pressure variations of about 2*10^-7 atmospheres.
            $endgroup$
            – Kyle
            yesterday










          • $begingroup$
            But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday






          • 2




            $begingroup$
            @SarveshThiruppathi If a sound wave is emitted for a long period of time, that means the source of the sound is vibrating for a long period of time. The wavelength would still be the same as if the same sound were emitted for a short period of time, so the vacuum you're imagining between waves wouldn't exist. What does make a difference is the volume (loudness) of the sound, which is why (roughly) there is a maximum possible volume which is reached when there is a vacuum between each wave.
            $endgroup$
            – dbmag9
            yesterday
















          $begingroup$
          Hi, Thanks for the answer , it was really helpful. I still have doubt in the last paragraph of your answer. Can you explain it with more details. Also I never said that sound wave is a transverse wave , by left and right i meant to - and - fro.
          $endgroup$
          – Sarvesh Thiruppathi
          yesterday




          $begingroup$
          Hi, Thanks for the answer , it was really helpful. I still have doubt in the last paragraph of your answer. Can you explain it with more details. Also I never said that sound wave is a transverse wave , by left and right i meant to - and - fro.
          $endgroup$
          – Sarvesh Thiruppathi
          yesterday












          $begingroup$
          Also , by 3 dimensional pattern , you mean a spherical kind of pattern , right ? But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre.
          $endgroup$
          – Sarvesh Thiruppathi
          yesterday




          $begingroup$
          Also , by 3 dimensional pattern , you mean a spherical kind of pattern , right ? But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre.
          $endgroup$
          – Sarvesh Thiruppathi
          yesterday




          1




          1




          $begingroup$
          @SarveshThiruppathi In a sense, yes, as the particles move apart it creates a low pressure region, but this acts as the restoring force to bring them back together. These pressure variations are usually very small, though. For example, a typical conversation between 2 people generates pressure variations of about 2*10^-7 atmospheres.
          $endgroup$
          – Kyle
          yesterday




          $begingroup$
          @SarveshThiruppathi In a sense, yes, as the particles move apart it creates a low pressure region, but this acts as the restoring force to bring them back together. These pressure variations are usually very small, though. For example, a typical conversation between 2 people generates pressure variations of about 2*10^-7 atmospheres.
          $endgroup$
          – Kyle
          yesterday












          $begingroup$
          But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop
          $endgroup$
          – Sarvesh Thiruppathi
          yesterday




          $begingroup$
          But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop
          $endgroup$
          – Sarvesh Thiruppathi
          yesterday




          2




          2




          $begingroup$
          @SarveshThiruppathi If a sound wave is emitted for a long period of time, that means the source of the sound is vibrating for a long period of time. The wavelength would still be the same as if the same sound were emitted for a short period of time, so the vacuum you're imagining between waves wouldn't exist. What does make a difference is the volume (loudness) of the sound, which is why (roughly) there is a maximum possible volume which is reached when there is a vacuum between each wave.
          $endgroup$
          – dbmag9
          yesterday




          $begingroup$
          @SarveshThiruppathi If a sound wave is emitted for a long period of time, that means the source of the sound is vibrating for a long period of time. The wavelength would still be the same as if the same sound were emitted for a short period of time, so the vacuum you're imagining between waves wouldn't exist. What does make a difference is the volume (loudness) of the sound, which is why (roughly) there is a maximum possible volume which is reached when there is a vacuum between each wave.
          $endgroup$
          – dbmag9
          yesterday











          9












          $begingroup$

          Sound wave is not a transverse wave, as you thought. That means the vibration and the direction of propagation for sound wave are parallel. And the vibration is caused by difference in air pressure at different places. To the question "how I can listen to it" thats because the pressure difference propagates toward your ear and force your eardrum to vibrate.






          share|cite|improve this answer








          New contributor




          user10842694 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.






          $endgroup$









          • 1




            $begingroup$
            Hi, I would like to point out two things from your answer. I never said a sound is a transverse wave. Also can you provide a explanation of how the sound wave propagated towards us.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday








          • 2




            $begingroup$
            Note, sound can be also a transverse wave, but only in solid materials (others don't have a shear stress). It has different properties than the longitudinal sound. This is how the internal properties of the Earth were discovered (liquid mantle, solid core). Also the electromagnetic and gravitational fields propagate as transverse waves.
            $endgroup$
            – peterh
            yesterday








          • 1




            $begingroup$
            "Sound wave is not a transverse wave, as you thought." This is nowhere in the OP's statement. As far as I'm concerned, this answer doesn't address the question at all.
            $endgroup$
            – knzhou
            19 hours ago










          • $begingroup$
            @knzhou I agree. -1. I'm not sure how this has gotten so many up votes
            $endgroup$
            – Aaron Stevens
            19 hours ago






          • 1




            $begingroup$
            @user10842694 I edited the question to make it a little clearer, but it was already clear in the first version that he wasn't asking "is sound a transverse wave". It blows my mind how half the answers here have answered that question instead.
            $endgroup$
            – knzhou
            19 hours ago
















          9












          $begingroup$

          Sound wave is not a transverse wave, as you thought. That means the vibration and the direction of propagation for sound wave are parallel. And the vibration is caused by difference in air pressure at different places. To the question "how I can listen to it" thats because the pressure difference propagates toward your ear and force your eardrum to vibrate.






          share|cite|improve this answer








          New contributor




          user10842694 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.






          $endgroup$









          • 1




            $begingroup$
            Hi, I would like to point out two things from your answer. I never said a sound is a transverse wave. Also can you provide a explanation of how the sound wave propagated towards us.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday








          • 2




            $begingroup$
            Note, sound can be also a transverse wave, but only in solid materials (others don't have a shear stress). It has different properties than the longitudinal sound. This is how the internal properties of the Earth were discovered (liquid mantle, solid core). Also the electromagnetic and gravitational fields propagate as transverse waves.
            $endgroup$
            – peterh
            yesterday








          • 1




            $begingroup$
            "Sound wave is not a transverse wave, as you thought." This is nowhere in the OP's statement. As far as I'm concerned, this answer doesn't address the question at all.
            $endgroup$
            – knzhou
            19 hours ago










          • $begingroup$
            @knzhou I agree. -1. I'm not sure how this has gotten so many up votes
            $endgroup$
            – Aaron Stevens
            19 hours ago






          • 1




            $begingroup$
            @user10842694 I edited the question to make it a little clearer, but it was already clear in the first version that he wasn't asking "is sound a transverse wave". It blows my mind how half the answers here have answered that question instead.
            $endgroup$
            – knzhou
            19 hours ago














          9












          9








          9





          $begingroup$

          Sound wave is not a transverse wave, as you thought. That means the vibration and the direction of propagation for sound wave are parallel. And the vibration is caused by difference in air pressure at different places. To the question "how I can listen to it" thats because the pressure difference propagates toward your ear and force your eardrum to vibrate.






          share|cite|improve this answer








          New contributor




          user10842694 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.






          $endgroup$



          Sound wave is not a transverse wave, as you thought. That means the vibration and the direction of propagation for sound wave are parallel. And the vibration is caused by difference in air pressure at different places. To the question "how I can listen to it" thats because the pressure difference propagates toward your ear and force your eardrum to vibrate.







          share|cite|improve this answer








          New contributor




          user10842694 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          share|cite|improve this answer



          share|cite|improve this answer






          New contributor




          user10842694 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          answered 2 days ago









          user10842694user10842694

          1152




          1152




          New contributor




          user10842694 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.





          New contributor





          user10842694 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.






          user10842694 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.








          • 1




            $begingroup$
            Hi, I would like to point out two things from your answer. I never said a sound is a transverse wave. Also can you provide a explanation of how the sound wave propagated towards us.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday








          • 2




            $begingroup$
            Note, sound can be also a transverse wave, but only in solid materials (others don't have a shear stress). It has different properties than the longitudinal sound. This is how the internal properties of the Earth were discovered (liquid mantle, solid core). Also the electromagnetic and gravitational fields propagate as transverse waves.
            $endgroup$
            – peterh
            yesterday








          • 1




            $begingroup$
            "Sound wave is not a transverse wave, as you thought." This is nowhere in the OP's statement. As far as I'm concerned, this answer doesn't address the question at all.
            $endgroup$
            – knzhou
            19 hours ago










          • $begingroup$
            @knzhou I agree. -1. I'm not sure how this has gotten so many up votes
            $endgroup$
            – Aaron Stevens
            19 hours ago






          • 1




            $begingroup$
            @user10842694 I edited the question to make it a little clearer, but it was already clear in the first version that he wasn't asking "is sound a transverse wave". It blows my mind how half the answers here have answered that question instead.
            $endgroup$
            – knzhou
            19 hours ago














          • 1




            $begingroup$
            Hi, I would like to point out two things from your answer. I never said a sound is a transverse wave. Also can you provide a explanation of how the sound wave propagated towards us.
            $endgroup$
            – Sarvesh Thiruppathi
            yesterday








          • 2




            $begingroup$
            Note, sound can be also a transverse wave, but only in solid materials (others don't have a shear stress). It has different properties than the longitudinal sound. This is how the internal properties of the Earth were discovered (liquid mantle, solid core). Also the electromagnetic and gravitational fields propagate as transverse waves.
            $endgroup$
            – peterh
            yesterday








          • 1




            $begingroup$
            "Sound wave is not a transverse wave, as you thought." This is nowhere in the OP's statement. As far as I'm concerned, this answer doesn't address the question at all.
            $endgroup$
            – knzhou
            19 hours ago










          • $begingroup$
            @knzhou I agree. -1. I'm not sure how this has gotten so many up votes
            $endgroup$
            – Aaron Stevens
            19 hours ago






          • 1




            $begingroup$
            @user10842694 I edited the question to make it a little clearer, but it was already clear in the first version that he wasn't asking "is sound a transverse wave". It blows my mind how half the answers here have answered that question instead.
            $endgroup$
            – knzhou
            19 hours ago








          1




          1




          $begingroup$
          Hi, I would like to point out two things from your answer. I never said a sound is a transverse wave. Also can you provide a explanation of how the sound wave propagated towards us.
          $endgroup$
          – Sarvesh Thiruppathi
          yesterday






          $begingroup$
          Hi, I would like to point out two things from your answer. I never said a sound is a transverse wave. Also can you provide a explanation of how the sound wave propagated towards us.
          $endgroup$
          – Sarvesh Thiruppathi
          yesterday






          2




          2




          $begingroup$
          Note, sound can be also a transverse wave, but only in solid materials (others don't have a shear stress). It has different properties than the longitudinal sound. This is how the internal properties of the Earth were discovered (liquid mantle, solid core). Also the electromagnetic and gravitational fields propagate as transverse waves.
          $endgroup$
          – peterh
          yesterday






          $begingroup$
          Note, sound can be also a transverse wave, but only in solid materials (others don't have a shear stress). It has different properties than the longitudinal sound. This is how the internal properties of the Earth were discovered (liquid mantle, solid core). Also the electromagnetic and gravitational fields propagate as transverse waves.
          $endgroup$
          – peterh
          yesterday






          1




          1




          $begingroup$
          "Sound wave is not a transverse wave, as you thought." This is nowhere in the OP's statement. As far as I'm concerned, this answer doesn't address the question at all.
          $endgroup$
          – knzhou
          19 hours ago




          $begingroup$
          "Sound wave is not a transverse wave, as you thought." This is nowhere in the OP's statement. As far as I'm concerned, this answer doesn't address the question at all.
          $endgroup$
          – knzhou
          19 hours ago












          $begingroup$
          @knzhou I agree. -1. I'm not sure how this has gotten so many up votes
          $endgroup$
          – Aaron Stevens
          19 hours ago




          $begingroup$
          @knzhou I agree. -1. I'm not sure how this has gotten so many up votes
          $endgroup$
          – Aaron Stevens
          19 hours ago




          1




          1




          $begingroup$
          @user10842694 I edited the question to make it a little clearer, but it was already clear in the first version that he wasn't asking "is sound a transverse wave". It blows my mind how half the answers here have answered that question instead.
          $endgroup$
          – knzhou
          19 hours ago




          $begingroup$
          @user10842694 I edited the question to make it a little clearer, but it was already clear in the first version that he wasn't asking "is sound a transverse wave". It blows my mind how half the answers here have answered that question instead.
          $endgroup$
          – knzhou
          19 hours ago











          7












          $begingroup$

          Sound travels outwards from a source in all directions. The waves that are set in motion are spherical.






          share|cite|improve this answer









          $endgroup$









          • 2




            $begingroup$
            Yes -- even though a 'speaker' may push air molecules in a certain direction, this just creates a volume of higher pressure air, which then expands in all directions.
            $endgroup$
            – amI
            yesterday
















          7












          $begingroup$

          Sound travels outwards from a source in all directions. The waves that are set in motion are spherical.






          share|cite|improve this answer









          $endgroup$









          • 2




            $begingroup$
            Yes -- even though a 'speaker' may push air molecules in a certain direction, this just creates a volume of higher pressure air, which then expands in all directions.
            $endgroup$
            – amI
            yesterday














          7












          7








          7





          $begingroup$

          Sound travels outwards from a source in all directions. The waves that are set in motion are spherical.






          share|cite|improve this answer









          $endgroup$



          Sound travels outwards from a source in all directions. The waves that are set in motion are spherical.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered 2 days ago









          niels nielsenniels nielsen

          20.4k53061




          20.4k53061








          • 2




            $begingroup$
            Yes -- even though a 'speaker' may push air molecules in a certain direction, this just creates a volume of higher pressure air, which then expands in all directions.
            $endgroup$
            – amI
            yesterday














          • 2




            $begingroup$
            Yes -- even though a 'speaker' may push air molecules in a certain direction, this just creates a volume of higher pressure air, which then expands in all directions.
            $endgroup$
            – amI
            yesterday








          2




          2




          $begingroup$
          Yes -- even though a 'speaker' may push air molecules in a certain direction, this just creates a volume of higher pressure air, which then expands in all directions.
          $endgroup$
          – amI
          yesterday




          $begingroup$
          Yes -- even though a 'speaker' may push air molecules in a certain direction, this just creates a volume of higher pressure air, which then expands in all directions.
          $endgroup$
          – amI
          yesterday











          6












          $begingroup$

          Re. from one of your comments: "But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre" and also this one: "But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop"



          I think part of you confusion comes from this: Even with a longitudinal wave where the particle motion is parallel to the waves propagation direction, the particles do not travel with the wave. They only move back and forth along the direction of wave propagation. So the particles are not carried along with the wave. (It is obvious that this is true for a transverse wave.)



          Referring to your original question, unless sound is focused into a beam it generally propagates equally in all directions. If it is focused into a beam and you were off to one side anything you hear would be due to sidelobes which are lower in amplitude than the main lobe and could be near zero.






          share|cite|improve this answer









          $endgroup$


















            6












            $begingroup$

            Re. from one of your comments: "But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre" and also this one: "But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop"



            I think part of you confusion comes from this: Even with a longitudinal wave where the particle motion is parallel to the waves propagation direction, the particles do not travel with the wave. They only move back and forth along the direction of wave propagation. So the particles are not carried along with the wave. (It is obvious that this is true for a transverse wave.)



            Referring to your original question, unless sound is focused into a beam it generally propagates equally in all directions. If it is focused into a beam and you were off to one side anything you hear would be due to sidelobes which are lower in amplitude than the main lobe and could be near zero.






            share|cite|improve this answer









            $endgroup$
















              6












              6








              6





              $begingroup$

              Re. from one of your comments: "But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre" and also this one: "But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop"



              I think part of you confusion comes from this: Even with a longitudinal wave where the particle motion is parallel to the waves propagation direction, the particles do not travel with the wave. They only move back and forth along the direction of wave propagation. So the particles are not carried along with the wave. (It is obvious that this is true for a transverse wave.)



              Referring to your original question, unless sound is focused into a beam it generally propagates equally in all directions. If it is focused into a beam and you were off to one side anything you hear would be due to sidelobes which are lower in amplitude than the main lobe and could be near zero.






              share|cite|improve this answer









              $endgroup$



              Re. from one of your comments: "But when the air molecule from the centre keeps moving away ,won't there be a vacuum created at the centre" and also this one: "But if the sound wave is emitted for long periods, wouldn't there be a complete vacuum and the sound wave would stop"



              I think part of you confusion comes from this: Even with a longitudinal wave where the particle motion is parallel to the waves propagation direction, the particles do not travel with the wave. They only move back and forth along the direction of wave propagation. So the particles are not carried along with the wave. (It is obvious that this is true for a transverse wave.)



              Referring to your original question, unless sound is focused into a beam it generally propagates equally in all directions. If it is focused into a beam and you were off to one side anything you hear would be due to sidelobes which are lower in amplitude than the main lobe and could be near zero.







              share|cite|improve this answer












              share|cite|improve this answer



              share|cite|improve this answer










              answered yesterday









              user45664user45664

              1,3152825




              1,3152825























                  4












                  $begingroup$

                  The revised question, as I understand it, amounts to asking how it is possible for a sound wave propagating along (instead of towards) a wall with a small hole in it to generate any sound waves on the other side of the hole. I have drawn a diagram of what I believe happens in this case:



                  Diagram of acoustic wave diffraction. A wall with a small hole in it divides the diagram horizontally in two halves.  In the top half of the diagram, a plane acoustic wave propagates horizontally past the hole.  In the bottom half, the hole acts as a point source for an expanding circular acoustic wave.



                  The hole bleeds off some of the acoustic energy of the plane wave, and uses it to generate a circular wave on the other side of the wall, as if it were a point source. This is an example of diffraction. I know for certain that this is what happens when the plane wave propagates toward the hole, and I think in this simple case the angle between the plane wave and the wall would only affect the intensity of the circular wave, but I'm not sure of that and the Wikipedia page on diffraction doesn't say anything about the angle. Can anyone confirm?



                  (N.B. A human's external ear has a much more complicated shape, which has evolved to efficiently gather sound waves passing the head in any direction and direct them into the ear canal, but the physical mechanism by which it does this is the same.)






                  share|cite|improve this answer









                  $endgroup$


















                    4












                    $begingroup$

                    The revised question, as I understand it, amounts to asking how it is possible for a sound wave propagating along (instead of towards) a wall with a small hole in it to generate any sound waves on the other side of the hole. I have drawn a diagram of what I believe happens in this case:



                    Diagram of acoustic wave diffraction. A wall with a small hole in it divides the diagram horizontally in two halves.  In the top half of the diagram, a plane acoustic wave propagates horizontally past the hole.  In the bottom half, the hole acts as a point source for an expanding circular acoustic wave.



                    The hole bleeds off some of the acoustic energy of the plane wave, and uses it to generate a circular wave on the other side of the wall, as if it were a point source. This is an example of diffraction. I know for certain that this is what happens when the plane wave propagates toward the hole, and I think in this simple case the angle between the plane wave and the wall would only affect the intensity of the circular wave, but I'm not sure of that and the Wikipedia page on diffraction doesn't say anything about the angle. Can anyone confirm?



                    (N.B. A human's external ear has a much more complicated shape, which has evolved to efficiently gather sound waves passing the head in any direction and direct them into the ear canal, but the physical mechanism by which it does this is the same.)






                    share|cite|improve this answer









                    $endgroup$
















                      4












                      4








                      4





                      $begingroup$

                      The revised question, as I understand it, amounts to asking how it is possible for a sound wave propagating along (instead of towards) a wall with a small hole in it to generate any sound waves on the other side of the hole. I have drawn a diagram of what I believe happens in this case:



                      Diagram of acoustic wave diffraction. A wall with a small hole in it divides the diagram horizontally in two halves.  In the top half of the diagram, a plane acoustic wave propagates horizontally past the hole.  In the bottom half, the hole acts as a point source for an expanding circular acoustic wave.



                      The hole bleeds off some of the acoustic energy of the plane wave, and uses it to generate a circular wave on the other side of the wall, as if it were a point source. This is an example of diffraction. I know for certain that this is what happens when the plane wave propagates toward the hole, and I think in this simple case the angle between the plane wave and the wall would only affect the intensity of the circular wave, but I'm not sure of that and the Wikipedia page on diffraction doesn't say anything about the angle. Can anyone confirm?



                      (N.B. A human's external ear has a much more complicated shape, which has evolved to efficiently gather sound waves passing the head in any direction and direct them into the ear canal, but the physical mechanism by which it does this is the same.)






                      share|cite|improve this answer









                      $endgroup$



                      The revised question, as I understand it, amounts to asking how it is possible for a sound wave propagating along (instead of towards) a wall with a small hole in it to generate any sound waves on the other side of the hole. I have drawn a diagram of what I believe happens in this case:



                      Diagram of acoustic wave diffraction. A wall with a small hole in it divides the diagram horizontally in two halves.  In the top half of the diagram, a plane acoustic wave propagates horizontally past the hole.  In the bottom half, the hole acts as a point source for an expanding circular acoustic wave.



                      The hole bleeds off some of the acoustic energy of the plane wave, and uses it to generate a circular wave on the other side of the wall, as if it were a point source. This is an example of diffraction. I know for certain that this is what happens when the plane wave propagates toward the hole, and I think in this simple case the angle between the plane wave and the wall would only affect the intensity of the circular wave, but I'm not sure of that and the Wikipedia page on diffraction doesn't say anything about the angle. Can anyone confirm?



                      (N.B. A human's external ear has a much more complicated shape, which has evolved to efficiently gather sound waves passing the head in any direction and direct them into the ear canal, but the physical mechanism by which it does this is the same.)







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                      share|cite|improve this answer



                      share|cite|improve this answer










                      answered 13 hours ago









                      zwolzwol

                      959615




                      959615























                          2












                          $begingroup$

                          You could use an explosion as a metaphor. The shockwaves "push" the air around in a spherical pattern, which then gets "sucked" back due to the low pressure left behind.



                          In a sense, soundwaves are just very slow and small shockwaves.



                          This video shows it really well.






                          share|cite|improve this answer








                          New contributor




                          Daniel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.






                          $endgroup$













                          • $begingroup$
                            +1 - was going to post an answer explaining it via explosion. But... you might consider taking out "just very slow and small shockwaves" and replacing it with, "smaller, and usually either repeated or patterned shockwaves - a musical note is just small shockwaves in a specific timing pattern." or similar.
                            $endgroup$
                            – Kevin
                            yesterday
















                          2












                          $begingroup$

                          You could use an explosion as a metaphor. The shockwaves "push" the air around in a spherical pattern, which then gets "sucked" back due to the low pressure left behind.



                          In a sense, soundwaves are just very slow and small shockwaves.



                          This video shows it really well.






                          share|cite|improve this answer








                          New contributor




                          Daniel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.






                          $endgroup$













                          • $begingroup$
                            +1 - was going to post an answer explaining it via explosion. But... you might consider taking out "just very slow and small shockwaves" and replacing it with, "smaller, and usually either repeated or patterned shockwaves - a musical note is just small shockwaves in a specific timing pattern." or similar.
                            $endgroup$
                            – Kevin
                            yesterday














                          2












                          2








                          2





                          $begingroup$

                          You could use an explosion as a metaphor. The shockwaves "push" the air around in a spherical pattern, which then gets "sucked" back due to the low pressure left behind.



                          In a sense, soundwaves are just very slow and small shockwaves.



                          This video shows it really well.






                          share|cite|improve this answer








                          New contributor




                          Daniel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.






                          $endgroup$



                          You could use an explosion as a metaphor. The shockwaves "push" the air around in a spherical pattern, which then gets "sucked" back due to the low pressure left behind.



                          In a sense, soundwaves are just very slow and small shockwaves.



                          This video shows it really well.







                          share|cite|improve this answer








                          New contributor




                          Daniel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.









                          share|cite|improve this answer



                          share|cite|improve this answer






                          New contributor




                          Daniel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.









                          answered yesterday









                          DanielDaniel

                          211




                          211




                          New contributor




                          Daniel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.





                          New contributor





                          Daniel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.






                          Daniel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                          Check out our Code of Conduct.












                          • $begingroup$
                            +1 - was going to post an answer explaining it via explosion. But... you might consider taking out "just very slow and small shockwaves" and replacing it with, "smaller, and usually either repeated or patterned shockwaves - a musical note is just small shockwaves in a specific timing pattern." or similar.
                            $endgroup$
                            – Kevin
                            yesterday


















                          • $begingroup$
                            +1 - was going to post an answer explaining it via explosion. But... you might consider taking out "just very slow and small shockwaves" and replacing it with, "smaller, and usually either repeated or patterned shockwaves - a musical note is just small shockwaves in a specific timing pattern." or similar.
                            $endgroup$
                            – Kevin
                            yesterday
















                          $begingroup$
                          +1 - was going to post an answer explaining it via explosion. But... you might consider taking out "just very slow and small shockwaves" and replacing it with, "smaller, and usually either repeated or patterned shockwaves - a musical note is just small shockwaves in a specific timing pattern." or similar.
                          $endgroup$
                          – Kevin
                          yesterday




                          $begingroup$
                          +1 - was going to post an answer explaining it via explosion. But... you might consider taking out "just very slow and small shockwaves" and replacing it with, "smaller, and usually either repeated or patterned shockwaves - a musical note is just small shockwaves in a specific timing pattern." or similar.
                          $endgroup$
                          – Kevin
                          yesterday











                          0












                          $begingroup$

                          There is more than one way to describe the amplitude of a sound wave. You can describe it as a displacement, in which case it's a vector with units of meters. On the other hand, you can also describe it as a pressure, which is a scalar with SI units of pascals.



                          It's possible to have a sound sensor whose response is proportional to the displacement, or one whose response is proportional to the pressure. The ear acts like the latter, because the eardrum is a membrane, and the membrane distorts in response to the pressure difference between the inner ear and the outside air. Therefore the ear is not sensitive to the direction in which the wave was propagating (although there are other cues that allow us to infer this for some frequencies, because we have binaural hearing).






                          share|cite|improve this answer









                          $endgroup$


















                            0












                            $begingroup$

                            There is more than one way to describe the amplitude of a sound wave. You can describe it as a displacement, in which case it's a vector with units of meters. On the other hand, you can also describe it as a pressure, which is a scalar with SI units of pascals.



                            It's possible to have a sound sensor whose response is proportional to the displacement, or one whose response is proportional to the pressure. The ear acts like the latter, because the eardrum is a membrane, and the membrane distorts in response to the pressure difference between the inner ear and the outside air. Therefore the ear is not sensitive to the direction in which the wave was propagating (although there are other cues that allow us to infer this for some frequencies, because we have binaural hearing).






                            share|cite|improve this answer









                            $endgroup$
















                              0












                              0








                              0





                              $begingroup$

                              There is more than one way to describe the amplitude of a sound wave. You can describe it as a displacement, in which case it's a vector with units of meters. On the other hand, you can also describe it as a pressure, which is a scalar with SI units of pascals.



                              It's possible to have a sound sensor whose response is proportional to the displacement, or one whose response is proportional to the pressure. The ear acts like the latter, because the eardrum is a membrane, and the membrane distorts in response to the pressure difference between the inner ear and the outside air. Therefore the ear is not sensitive to the direction in which the wave was propagating (although there are other cues that allow us to infer this for some frequencies, because we have binaural hearing).






                              share|cite|improve this answer









                              $endgroup$



                              There is more than one way to describe the amplitude of a sound wave. You can describe it as a displacement, in which case it's a vector with units of meters. On the other hand, you can also describe it as a pressure, which is a scalar with SI units of pascals.



                              It's possible to have a sound sensor whose response is proportional to the displacement, or one whose response is proportional to the pressure. The ear acts like the latter, because the eardrum is a membrane, and the membrane distorts in response to the pressure difference between the inner ear and the outside air. Therefore the ear is not sensitive to the direction in which the wave was propagating (although there are other cues that allow us to infer this for some frequencies, because we have binaural hearing).







                              share|cite|improve this answer












                              share|cite|improve this answer



                              share|cite|improve this answer










                              answered 11 hours ago









                              Ben CrowellBen Crowell

                              52.6k6162306




                              52.6k6162306























                                  0












                                  $begingroup$

                                  While the mean air motion of the wave is in one direction (assuming a plane wave), the air molecules actually move in all directions. They are in local thermal equilibrium (due to frequent randomizing collisions), which is what gives meaning to pressure as the basis for modeling acoustics. This random molecular motion in all directions is at speeds of order the speed of sound, hundreds of meters per second.



                                  The mean motion (longitudinal) is an oscillating displacement of micrometers or less for typical sounds, at kilohertz frequencies, corresponding to a speed of millimeters per second at most. It can be much less for faint sounds. The ear is a remarkably sensitive detector!



                                  The ear canal is smaller than the wavelengths of audible sound. Thus, as sound passes by in any direction, the ear mainly responds to the pressure oscillations without regard to the direction of the wave. When a pressure peak surrounds the ear, air is (slightly) pumped into the ear, due to the random motions that equilibrate pressure. When a trough surrounds the ear, air is (slightly) sucked out of the ear. This happens at the frequency of the sound (say a thousand times per second), vibrating the eardrum.



                                  Zwol's answer correctly notes that this can be seen as an instance of diffraction. It is a limit in which the hole is so small that the pressure at any instant is nearly uniform over the hole, so diffraction through the hole is nearly independent of the incident angle.






                                  share|cite|improve this answer









                                  $endgroup$


















                                    0












                                    $begingroup$

                                    While the mean air motion of the wave is in one direction (assuming a plane wave), the air molecules actually move in all directions. They are in local thermal equilibrium (due to frequent randomizing collisions), which is what gives meaning to pressure as the basis for modeling acoustics. This random molecular motion in all directions is at speeds of order the speed of sound, hundreds of meters per second.



                                    The mean motion (longitudinal) is an oscillating displacement of micrometers or less for typical sounds, at kilohertz frequencies, corresponding to a speed of millimeters per second at most. It can be much less for faint sounds. The ear is a remarkably sensitive detector!



                                    The ear canal is smaller than the wavelengths of audible sound. Thus, as sound passes by in any direction, the ear mainly responds to the pressure oscillations without regard to the direction of the wave. When a pressure peak surrounds the ear, air is (slightly) pumped into the ear, due to the random motions that equilibrate pressure. When a trough surrounds the ear, air is (slightly) sucked out of the ear. This happens at the frequency of the sound (say a thousand times per second), vibrating the eardrum.



                                    Zwol's answer correctly notes that this can be seen as an instance of diffraction. It is a limit in which the hole is so small that the pressure at any instant is nearly uniform over the hole, so diffraction through the hole is nearly independent of the incident angle.






                                    share|cite|improve this answer









                                    $endgroup$
















                                      0












                                      0








                                      0





                                      $begingroup$

                                      While the mean air motion of the wave is in one direction (assuming a plane wave), the air molecules actually move in all directions. They are in local thermal equilibrium (due to frequent randomizing collisions), which is what gives meaning to pressure as the basis for modeling acoustics. This random molecular motion in all directions is at speeds of order the speed of sound, hundreds of meters per second.



                                      The mean motion (longitudinal) is an oscillating displacement of micrometers or less for typical sounds, at kilohertz frequencies, corresponding to a speed of millimeters per second at most. It can be much less for faint sounds. The ear is a remarkably sensitive detector!



                                      The ear canal is smaller than the wavelengths of audible sound. Thus, as sound passes by in any direction, the ear mainly responds to the pressure oscillations without regard to the direction of the wave. When a pressure peak surrounds the ear, air is (slightly) pumped into the ear, due to the random motions that equilibrate pressure. When a trough surrounds the ear, air is (slightly) sucked out of the ear. This happens at the frequency of the sound (say a thousand times per second), vibrating the eardrum.



                                      Zwol's answer correctly notes that this can be seen as an instance of diffraction. It is a limit in which the hole is so small that the pressure at any instant is nearly uniform over the hole, so diffraction through the hole is nearly independent of the incident angle.






                                      share|cite|improve this answer









                                      $endgroup$



                                      While the mean air motion of the wave is in one direction (assuming a plane wave), the air molecules actually move in all directions. They are in local thermal equilibrium (due to frequent randomizing collisions), which is what gives meaning to pressure as the basis for modeling acoustics. This random molecular motion in all directions is at speeds of order the speed of sound, hundreds of meters per second.



                                      The mean motion (longitudinal) is an oscillating displacement of micrometers or less for typical sounds, at kilohertz frequencies, corresponding to a speed of millimeters per second at most. It can be much less for faint sounds. The ear is a remarkably sensitive detector!



                                      The ear canal is smaller than the wavelengths of audible sound. Thus, as sound passes by in any direction, the ear mainly responds to the pressure oscillations without regard to the direction of the wave. When a pressure peak surrounds the ear, air is (slightly) pumped into the ear, due to the random motions that equilibrate pressure. When a trough surrounds the ear, air is (slightly) sucked out of the ear. This happens at the frequency of the sound (say a thousand times per second), vibrating the eardrum.



                                      Zwol's answer correctly notes that this can be seen as an instance of diffraction. It is a limit in which the hole is so small that the pressure at any instant is nearly uniform over the hole, so diffraction through the hole is nearly independent of the incident angle.







                                      share|cite|improve this answer












                                      share|cite|improve this answer



                                      share|cite|improve this answer










                                      answered 6 hours ago









                                      nanomannanoman

                                      1511




                                      1511






















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