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This guide provides current information and equations for calculating the speed of sound in pure water as a function of temperature and pressure.


Speed of sound as a function of temperature only

* Bilaniuk and Wong's equations
  Del Grosso and Mader's (1972) data re-calculated following adoption of the International Temperature Scale of 1990
* Marczak's equation
  A fifth order polynomial derived from the combined data of Del Grosso and Mader (1972), Kroebel and Mahrt (1976) and Fujii and Masui (1993)
* Lubbers and Graaff's simplified equation
  A simple equation valid for a limited temperature range

Which Equation?

Differences between the Bilaniuk and Wong 148 point equation and Marczak's equation are of the order of 0.02 ms-1 or better at most temperatures, and either equation is suitable for the most accurate work. The Marczak equation has the advantage that all coefficients are expressed to 6 decimal places rather than the 8 decimal places of Bilaniuk and Wong.

Speed of sound as a function of temperature and pressure

* The equation of Belogol'skii, Sekoyan et al
  The pressure dependence of sound speed in distilled water

Also available:

For further information, contact Stephen Robinson

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