Two pulses set off together down 343 m of track. One is your gas at your temperature; the other is always dry air at 20 °C. Whatever pulls ahead or falls behind is the whole story of v = sqrt(γRT/M).
Speed of sound v = sqrt(γRT/M)
343.2 m/s
1.00× dry air at 20 °C
Mach 1
1236 km/h
Mach 1 (mph)
768 mph
440 Hz note
78.0 cm
Time over 1 km
2.91 s
Temperature20 °C
Gasair
Humidity0% RH
Air: γ = 1.400 · M = 28.96 g/mol
No pressure control — on purpose. Squeezing a gas raises its pressure and its density together, and in v = sqrt(γRT/M) the two cancel exactly. Pressure alone does not change the speed of sound.
Tip: swap air for helium and watch the gold pulse finish first — a molar mass seven times smaller beats anything the temperature slider can do.