The speed of sound at different tempertures

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Homework Help Overview

The discussion revolves around the relationship between the speed of sound and temperature, particularly questioning how sound speed behaves as temperature approaches absolute zero. The original poster expresses confusion regarding the effects of density and particle motion on sound speed in this context.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand the relationship between density, temperature, and sound speed, questioning whether sound speed increases as temperature decreases. Some participants provide links to resources that discuss equations related to sound speed in air, while others raise concerns about the applicability of these equations at very low temperatures.

Discussion Status

Participants are exploring different interpretations of how temperature affects sound speed, with some guidance offered through external resources. There is an acknowledgment of the limitations of certain equations when applied to extreme temperatures, but no consensus has been reached on the original poster's question.

Contextual Notes

There is a mention of the temperature range for which certain equations are valid, specifically noting that the equations may not hold accuracy at temperatures significantly below 0 degrees Celsius. This raises questions about the assumptions underlying the models discussed.

gateman234
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Homework Statement


does the speed of sound increase as the temperture becomes closer to absolute zero, which would make the substance more and more dense?


Homework Equations


dont think there is any


The Attempt at a Solution



really confused as, isn't it the more dense a substance is the faster sound travels as particle colisions are faster, but while the temperture decreases the particle don't move as much
 
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Check this page out. There's a simple equation that models the temperature dependence of sound in air (I assume you're talking about air and not some other substance).

http://www.glenbrook.k12.il.us/gbssci/Phys/Class/sound/u11l2c.html
 
Last edited by a moderator:
But the disclaimer says:
The above equation relating the speed of a sound wave in air to the temperature provides reasonably accurate speed values for temperatures between 0 and 100 Celsius. The equation itself does not have any theoretical basis; it is simply the result of inspecting temperature-speed data for this temperature range.

And as he's talking about going 273 degrees below 0, it won't hold accuracy.
 
Ah, I read the OP wrong. I was thinking he was going to 0 C.

Look instead at the following page.

http://en.wikipedia.org/wiki/Speed_of_sound

In the section entitled "Speed in ideal gases and in air" they give an expression for c_{ideal}, the speed of sound in an ideal gas as a function of temperature (this temperature is in Kelvins). This equation applies down to absolute zero.

From the first website I gave you:

The equation itself does not have any theoretical basis; it is simply the result of inspecting temperature-speed data for this temperature range.

It would seem that this statement is wrong, because the Wiki page does in fact derive it as an approximation of the earlier expression for c_{ideal}, which comes from the ideal gas law!
 

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