High pressure vs speed of sound?

[iminhell]

I understand that for normal atmospheric conditions the speed of sound is relative to the temperature. I also understand that the equation uses the input temperature to first figure the density of air. But my question has to do with the effect of high pressure, we'll say above atmospheric to 1,000psi.
Will the speed of sound change because the molecules of air are now more tightly packed in our constant volume and there by their Mean Free Path is less? (meaning that following the temperature model the speed of sound should slow and pressure increases above atmospheric)
Can the speed of sound in air be determined solely from the Mean Free Path?

I've been searching for 2 days now for this answer and have been unable to find one. I did find work by a Martin Greenspan for the speed of sound in vacuum/partial vacuum. But I'm not sure if it applies to air or pressure situations.

Looking for the information pretty much to settle a bet with myself. We tend to argue. More so now that he hasn't been sleeping well and I have.

 

[cjl]

For an ideal gas, the sound speed is dependent exclusively on temperature. This will deviate somewhat for a real gas, but not all that much. I haven't looked into it, but my guess would be that the effect of pressure up to 1kpsi is pretty much negligible.