# Homework Help: The speed of sound at different tempertures

1. Apr 3, 2008

### gateman234

1. The problem statement, all variables and given/known data
does the speed of sound increase as the temperture becomes closer to absolute zero, which would make the substance more and more dense?

2. Relevant equations
dont think there is any

3. The attempt at a solution

really confused as, isnt it the more dense a substance is the faster sound travels as particle colisions are faster, but while the temperture decreases the particle dont move as much

2. Apr 3, 2008

### Tom Mattson

Staff Emeritus
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 [Broken]

Last edited by a moderator: May 3, 2017
3. Apr 3, 2008

### nonequilibrium

But the disclaimer says:
And as he's talking about going 273 degrees below 0, it won't hold accuracy.

4. Apr 3, 2008

### Tom Mattson

Staff Emeritus
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:

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!