If sound hits a solid object and enters it,can the longitudinal sound wave in air transform into transversal or extensional wave in solid? Or is it that longitudinal wave will always stay longitudinal even if it transitions from gas into solid?

For example,if I am calculating reflection when sound hits object made from aluminum,I need to know the impedance difference.Impedance is sound velocity times mass.

Aluminum have longitudinal velocity of 6420 m/s,but transversal sound velocity is only 3020 m/s,so I dont know if I can just ignore the transversal and extensional velocities and only focus on longitudinal velocity becose sound waves in air can be only longitudonal,or can in some specific angle,or geometry,or something,sound in wave hit aluminum and create non-longitudinal waves inside it?

  • 1
    $\begingroup$ Can non-longitudinal sound waves in solids induce sound in air? Yes. Then the converse is also true by time-reversal symmetry. $\endgroup$
    – Hussein
    Mar 3, 2018 at 20:31

1 Answer 1


If you have a thin, flexible sheet and hit it face-on with a sound wave, then the sound wave will introduce transverse waves in the sheet as it pushes it back and forth.

  • $\begingroup$ Are you sure? Arent microphone diaphragms traveling in pistonic motion? $\endgroup$ Mar 1, 2018 at 6:41
  • $\begingroup$ Pistonic motion is apparently meant to eliminate precisely those transverse bending modes that I had assumed would drive the diaphragm. Seems I was misinformed about how diaphragm microphones work. In any case, what I said about a thin, flexible sheet in general is still true. $\endgroup$ Mar 2, 2018 at 5:34

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