Density does not affect the speed of sound of a gas. Temperature and molar mass does. So increasing the pressure of a given composition of gas won’t change anyt

Density does not affect the speed of sound of a gas. Temperature and molar mass does. So increasing the pressure of a given composition of gas won’t change anything, assuming you can bring the temp back down. Helium is obviously a different molar mass. But also dry air vs moist air can have an effect.