The calculator presented here computes the zero-frequency speed of sound in humid air according to Cramer (J. Acoust. Soc. Am., 93, p2510, 1993), with saturation vapour pressure taken from Davis, Metrologia, 29, p67, 1992, and a mole fraction of carbon dioxide of 0.0004.
Range of validity: the calculator is only valid over the temperature range 0 to 30 ° C (273.15 - 303.15 K) and for the pressure range 75 - 102 kPa
Please note that NPL no longer carries out work in airborne acoustics, so we are unable to answer technical queries.