Question

Do sound waves travel better through hot or cold gases?

Answer 1

Its gases, not glasses.
The speed of sound is given by\[v=\sqrt{\frac{dP}{d\rho}}=\sqrt{\gamma\frac{P}{\rho}}\] Considering that the vibrations are adiabatic.
Now, a gas with mass M and molecular mass m follows the formula\[PV=\frac{M}{m}RT\]\[P=\left(\frac{M}{V}=\rho\right)\frac{RT}{m}\]\[\frac{P}{\rho}=\frac{RT}{m}\]\[v=\sqrt{\frac{\gamma RT}{m}}\]Therefore, the speed of sound increases with temperature in ideal gases. The physical explanation for that, is that as the temperature increases, there is more kinectic energy in the particles of the gas, and since the sound is the vibration of those particles, the faster they move the faster the sound propagates.