Why is speed of sound constant?

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Discussion Overview

The discussion centers around the question of why the speed of sound is considered constant in an ideal gas, exploring the relationship between the speed of sound and the behavior of gas particles in response to oscillations from a diaphragm.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions why the speed of sound is constant in an ideal gas, suggesting that if a diaphragm moves at ~3000 m/s, the pressure wave should also travel at that speed due to elastic collisions with gas particles.
  • Another participant indicates that the analysis of the speed of sound is more complex than the initial suggestion implies.
  • A different participant notes that while the speed of sound is comparable to the RMS speed of gas molecules, the RMS speed due to thermal motion is typically much greater than the speed of the diaphragm's movement.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the explanation for the constancy of the speed of sound, with multiple viewpoints and complexities presented.

Contextual Notes

The discussion highlights the need for a deeper analysis of the relationship between particle speeds and sound propagation, indicating potential limitations in the initial assumptions made about elastic collisions and energy transfer.

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This just occurred to me a few minutes ago, sorry if it's a dumb question:'

Why is the speed of sound constant in an ideal gas?

Suppose you have a box with an ideal mono atomic gas and a diaphragm that can oscillate. The diaphragm busts one move at ~3000 m/s. Since collisions with ideal gas particles are modeled elastically, the RMS speed of the particles that were in contact with the diaphragm while moving is ~3000m/s. Consequently, the neighboring particles will be bumped to ~3000m/s also, and so on until the end of the box is reached. Since no energy is lost and the RMS speed in the other two dimensions is zero, won't the pressure wave be traveling at ~3000m/s?
 
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The analysis is a little more complex.

http://www.grc.nasa.gov/WWW/K-12/airplane/snddrv.html"
 
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By the way, the speed of sound is of the same order as the RMS speed of molecules in the gas, but the original RMS speed of molecules due to thermal motion is going to be much greater than the speed at which the diaphragm is moving.
 
thank you (teşekkür ederim)
 

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