Density and pressure are much alike, both are related to the spacing between the particles of an object, Density decreases with higher heat, as does pressure,oh yeah, what does a Barometer measure? AIR PRESSURE, not air density, so yeah, we both are right, Temperature and Pressure are both factors in the speed of sound. Higher pressure and lower temperature go together to make a high speed of sound. Opposite is true for high speed of sound.