Speed of sound in pure water as a function of temperature

In view of the adoption of the International Temperature Scale of 1990 (ITS-90), which defines the International Celsius Temperatures, t90, the dependence on temperature of the speed of sound in pure water is examined. Drawing on the experimental data published previously by Del Grosso and Mader [J. Acoust. Soc. Am. 52, 1442–1446 (1972)], it is found that the change from the previous t68 scale is significant. At 100 °C, the difference between the two scales (t68–t90) is 0.026 °C, resulting in a difference of 0.022 m/s for the speed of sound. The speed of sound is fitted to a new fifth-order polynomial applicable over the t90 range 0–100 °C.