Is it true that we can speak, sing and play wind (brass) musical instruments due to the existence of the Bernoulli's Principle ?


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  • $\begingroup$ It would help to know why you think this $\endgroup$ – Aaron Stevens Mar 15 at 12:35
  • $\begingroup$ I ask this, not think. $\endgroup$ – Aleksey Druggist Mar 15 at 12:41
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    $\begingroup$ Right, but why do you think it might be true? (I assume you wouldn't ask if you didn't think there was a connection.) As it stands, it's like asking "is it true that we can walk due to conservation of energy?" The two phenomena are part of the same field of physics, and there's probably a connection that could be drawn, but without more information about how you're thinking about it, an answer might not be useful. $\endgroup$ – Michael Seifert Mar 15 at 13:00
  • $\begingroup$ @MichaelSeifert I agree, but I have taken a stab at it nonetheless. $\endgroup$ – Aaron Stevens Mar 15 at 13:09
  • $\begingroup$ @Michael Seifert, is this a trick question? It seems to me that we can walk due to the existence of a non-conservative friction force) $\endgroup$ – Aleksey Druggist Mar 15 at 13:40

I think by mentioning Bernoulli you are mostly thinking of sounds and voices created by wind flow. Otherwise there are some sounds that are created by clicking the teeth or other means.

Our vocal cords are the gate way to high pressure wind created in our longs by contraction of the rib cage and moving of the diaphragm.

Our vocal cords have range of vibration that can produce human voice with a range of roughly 85 to 180 Hz and female voice one octave higher at about 165 to 255 Hz, according to Wikipedia.

The way our vocal cords control sound is by blocking the air flow from our longs and releasing it in blasts of shockwaves which will be amplified in our mouth and modified by the tongue and lips and changing the geometry of our voice box and forming our throat like a trombone.

The Bernoulli law among other things is a what happens at the sharp edge of the vocal cords.

Hi pressure air blocked by the cord, when released by the cord slit opening, accelerates into a fast moving shockwave(Bernoulli law) with a reduced pressure which makes it easy for the cord to close back or tighten the slit. This release of shockwave repeats itself to make the note blown out.

This compression and decompression behind the vocal cord is a hormonic vibration which we have learned to control and make it into words or songs.

This is just a very basic version of a very complex phenomena.


Bernoulli's principal is essentially just energy conservation or Newton's laws applied to fluid flow. So really this comes down to is Newtonian mechanics important for these processes. I say to this that most macroscopic, mechanical processes rely on Newton's laws. Here we have forces acting on fluids, so I would say it applies. This is as specific as I can be, since Newton's laws cover so many phenomena, and the question does not ask for any specifics.

One example I can think of though is if someone were to speak, sing, play the trumpet, etc. the diaphragm has to move to change the pressure acting on air in the lungs. This causes air to move from the higher to lower pressure region, thus the air speeds up and moves out if the lungs through the "instrument".

In contrast the actual sounds that are produced more rely on the properties of standing waves in the instrument, waves in the air, and our perception of those waves. However you could argue that some of that also has Bernoulli hidden within I suppose. Like I said, it's all just Newton's laws and energy conservation.

  • $\begingroup$ ..."the diaphragm has to move to change the pressure acting on air in the lungs" ... The diaphragm can move with sound frequencies? $\endgroup$ – Aleksey Druggist Mar 15 at 13:57
  • $\begingroup$ @AlekseyDruggist I don't think I understand your question $\endgroup$ – Aaron Stevens Mar 15 at 14:03
  • $\begingroup$ @ Aaron Stevens I understand from your answer that the diaphragm is the element that oscillates with sound frequency, generating sound waves $\endgroup$ – Aleksey Druggist Mar 15 at 14:09
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    $\begingroup$ @aleksey the diaphragm simply pushes the air. The vibrations come from some other element along the way: your vocal cords, your lips, the instrument's reed, etc. $\endgroup$ – Javier Mar 15 at 14:30
  • $\begingroup$ @AlekseyDruggist the above comment is correct. The diaphragm does not directly cause the oscillations of sound. $\endgroup$ – Aaron Stevens Mar 15 at 14:44

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