.... why does an increase in temperature mean an increase in the speed of
sound?

That's got me confused. Hotter = less dense.

Thanks in advance.

"xerj" > wrote in message
...
> ... why does an increase in temperature mean an increase in the speed of
> sound?

Because density is not the sole determining factor for the sound of speed
through some medium.

Got it.

Found a page that explains it :-

http://www.newton.dep.anl.gov/askasci/phy00/phy00826.htm


"Peter Duniho" > wrote in message
...
> "xerj" > wrote in message
> ...
>> ... why does an increase in temperature mean an increase in the speed of
>> sound?
>
> Because density is not the sole determining factor for the sound of speed
> through some medium.
>

"xerj" > wrote in message
...
>
> ... why does an increase in temperature mean an increase in the speed of
> sound?
>
> That's got me confused. Hotter = less dense.
>
> Thanks in advance.

The speed of sound varies with temperature alone.

In article t>,
"Steven P. McNicoll" > wrote:

> "xerj" > wrote in message
> ...
> >
> > ... why does an increase in temperature mean an increase in the speed of
> > sound?
> >
> > That's got me confused. Hotter = less dense.
> >
> > Thanks in advance.
>
> The speed of sound varies with temperature alone.

The speed of sound varies with temperature and type of medium.

--
Bob Noel
New NHL? what a joke

Bob Noel wrote:

>>> Thanks in advance.
>> The speed of sound varies with temperature alone.
>
> The speed of sound varies with temperature and type of medium.
>
The speed of sound in air varies almost solely with
temperature. For other types of mediums, the temperature is
less of a factor. The general formula for the speed of sound
is the density divided by the bulk modulus. The issue is that
with gases the other variables in the equation all cancel each
other out.

In water for example, density is a MAJOR factor. The speed
of sound in salt water is faster than fresh water in addition
to temperature.

"Ron Natalie" > wrote in message
m...
> Bob Noel wrote:
>
>>>> Thanks in advance.
>>> The speed of sound varies with temperature alone.
>>
>> The speed of sound varies with temperature and type of medium.
>>
> The speed of sound in air varies almost solely with
> temperature. For other types of mediums, the temperature is
> less of a factor. The general formula for the speed of sound
> is the density divided by the bulk modulus. The issue is that
> with gases the other variables in the equation all cancel each
> other out.
>
> In water for example, density is a MAJOR factor. The speed
> of sound in salt water is faster than fresh water in addition
> to temperature.

You're mixing apples and oranges. Water (H2O) does not equal salt water
(H2O + NaCl). They are two different media. Just as air is a nominal mix
of N + O + a few other gasses. Change that mix and it's a different media
with a different gamma and bulk modulus (R). So your density change is
really a change in media.

If the media doesn't change, density doesn't have an effect on the speed of
sound. Changing the media changes the gamma and R; but for any one specific
media, only temperature will cause a change in the speed of sound.

Gerry

Ron Natalie wrote:
> Bob Noel wrote:
>
>>>> Thanks in advance.
>>>
>>> The speed of sound varies with temperature alone.
>>
>>
>> The speed of sound varies with temperature and type of medium.
>>
> The speed of sound in air varies almost solely with
> temperature. For other types of mediums, the temperature is
> less of a factor. The general formula for the speed of sound
> is the density divided by the bulk modulus. The issue is that
> with gases the other variables in the equation all cancel each
> other out.
>
> In water for example, density is a MAJOR factor. The speed
> of sound in salt water is faster than fresh water in addition
> to temperature.

Commpressibility is the major factor. Water isn't very compressible
and transmits sound quite well, but air is and sound dissipates.
Frequency dispersion which has to do with how well various frequencies
are transmitted, affects how much the receiver will understand what is
being sent. It is an exceedingly complicated phenomenom -- ask any
sonar designer or a Navy weapons person.

"Bob Noel" > wrote in message
...
>
> The speed of sound varies with temperature and type of medium.
>

The medium under discussion per the subject line is air. Since this is a
piloting group it can be reasonably assumed to be air at temperatures found
in the atmosphere. Air at atmospheric temperatures behaves as an ideal gas
and the speed of sound in an ideal gas is a function of temperature.

Deriving the sonic velocity is one favorite question for the final exam
of mechanical engineering thermodynamics courses. From my old
textbook:

"in an ideal gas the sonic velocity depends only on the molecular
weight and the absolute temperature (degF + 460), and is proportional
to the square root of that absolute temperature".

On 17 Dec 2005 09:45:07 -0800, "nrp" > wrote in
. com>::

>"in an ideal gas the sonic velocity depends only on the molecular
>weight and the absolute temperature (degF + 460), and is proportional
>to the square root of that absolute temperature".

In which units does that equation provide the sonic velocity?

More here:
http://roger.ecn.purdue.edu/~aerodyn/AAE334/FALL05/html/Lectures/Lecture06.html

When I took thermo, there were only ft lbs, BTUs, and lbm. It was a
lot simpler before Metric became PC. (I wonder how we happened to keep
seconds?)

"nrp" > wrote in message
oups.com...
>
> When I took thermo, there were only ft lbs, BTUs, and lbm. It was a
> lot simpler before Metric became PC.
>

I found the MKS system to be simpler.

nrp wrote:
> When I took thermo, there were only ft lbs, BTUs, and lbm. It was a
> lot simpler before Metric became PC. (I wonder how we happened to keep
> seconds?)
>

You must be REALLY old as the SI system has been around at least since
1875. :-)


Matt

On 17 Dec 2005 12:07:43 -0800, "nrp" > wrote in
. com>::

>When I took thermo, there were only ft lbs, BTUs, and lbm.

So you don't know if your equation expresses sonic velocity in knots
or MPH?

In hotter air the molecules can move faster, so they carry disturbances
(sound waves) faster.

In denser substances such as water and steel, the molecules do not move
far from a central point so the increased temperature does not give
them the opportunity to transmit the sound disturbance at a faster rate
when heated.

However, because of the greater density and the fact that molecules are
closer together in water and steel than in air, sound does travel
faster in water and steel than in air. The closer the molecules are
together, the more quickly a disturbance is transmitted from one
molecule to another.

Larry Dighera wrote:
> On 17 Dec 2005 12:07:43 -0800, "nrp" > wrote in
> . com>::
>
> >When I took thermo, there were only ft lbs, BTUs, and lbm.
>
> So you don't know if your equation expresses sonic velocity in knots
> or MPH?