Pressure

[tigerthakur]

if pressure increases then the speed of sound

[Old_Geezer]

It temperature drops then the age of man

[wiltsman]

Is there more to come?

[sandyRoe]

slows?

[heathfield]

...will stay the same. The speed of sound in air depends on air temperature, not pressure. The lower the temperature, the slower the speed of sound.

[smurfchops]

heathfield you should be an interpreter.

[Peter Pedant]

Heathie:
but the speed of LIGHT in a gas does depend on pressure doesnt it?
(I agree that isnt the q asked)
which is why you can 'see' blast waves isnt it ?

( thanks ) PP

[jim360]

Whoops, healthfield - Don't forget that pressure itself depends on temperature via pV = NkT where k = Boltzmann constant, so that if anything depends on temperature it may also depend on pressure.

The precise dependence is determined by the law involved - the general relationship is c^2 = dp/dr where c = speed of sound, p = pressure and r = density. In general sound speed increases with pressure.

[jim360]

Should add that while in general there is a pressure dependence, in the ideal case this does vanish.

[jomifl]

The speed of sound increases with density. Temperature and pressure may influence the density but do not of themselves influence the speed of sound.

[jim360]

In ideal gases it's temperature. My post earlier was strictly correct but overcomplicated things. The law in ideal gases is:

"sound speed squared is directly proportional to temperature"

, with only variables cancelling through the ideal gas law. In non-ideal gases pressure and density can play a weaker role.

[wildwood]

Great answers to a non-question. :-)

[jim360]

Apologies to heathfield for implying that he was wrong when he was not. I should have checked my memory and notes better.

[heathfield]

Noooo problem, Jim. Just something I remembered from my school days!