Speed of Sound in Air vs Temperature

Scopec = 331.3 sqrt(1 + T_C/273.15) m/s (dry air, from c = sqrt(gamma R T / M)), converted to ft/s. It swings about 6% over a working day -- 1,087 ft/s at 32 F, 1,126 ft/s at 68 F, 1,155 ft/s at 95 F -- and since the required delay at a fixed distance is inversely proportional to c, re-timing an outdoor delay tower for the day's temperature keeps arrivals aligned. Reports the speed in ft/s and m/s and the propagation delay (1000/c, about 0.888 ms/ft at 68 F). Dry air; humidity is a small second-order correction and altitude alone does not change it. A first-principles aid (kinetic theory / NIST); the measured tuning governs.

Formula or tablec = 331.3 sqrt(1 + T_C/273.15) m/s (dry air, from c = sqrt(gamma R T / M)); ft/s = m/s x 3.28084; propagation delay = 1000 / c_ftps ms per foot. T_C = (T_F - 32)/1.8.

Source and editionFirst-principles kinetic theory (c = sqrt(gamma R T / M)) with the NIST/standard 331.3 m/s dry-air reference at 0 C, by name.

Free accessThe speed-of-sound-vs-temperature relation is public first-principles physics; the 331.3 m/s reference at 0 C is a standard NIST value and the air temperature is the user's input.

What governsEstimate. AHJ and licensed professional govern.

API field namestemperature_f, speed_ftps, delay_ms_per_ft

• Speed of sound c = 331.3 sqrt(1 + T_C/273.15) m/s (dry air), from c = sqrt(gamma R T / M)kinetic theory / NIST
• Propagation delay 1000 / c_ftps ms per foot; delay is inversely proportional to cacoustics
• Dry air humidity is a small second-order correction; altitude alone does not change cscope of this tile